also update internal names

com.unity.ml-agents/Runtime/Sensors/BoxOverlapChecker.cs

         bool m_RotateWithAgent;
         LayerMask m_ColliderMask;
         GameObject m_CenterObject;
-        GameObject m_RootReference;
+        GameObject m_AgentGameObject;
         string[] m_DetectableTags;
         int m_InitialColliderBufferSize;
         int m_MaxColliderBufferSize;
             bool rotateWithAgent,
             LayerMask colliderMask,
             GameObject centerObject,
-            GameObject rootReference,
+            GameObject agentGameObject,
             string[] detectableTags,
             int initialColliderBufferSize,
             int maxColliderBufferSize)
             m_RotateWithAgent = rotateWithAgent;
             m_ColliderMask = colliderMask;
             m_CenterObject = centerObject;
-            m_RootReference = rootReference;
+            m_AgentGameObject = agentGameObject;
             m_DetectableTags = detectableTags;
             m_InitialColliderBufferSize = initialColliderBufferSize;
             m_MaxColliderBufferSize = maxColliderBufferSize;
                 var currentColliderGo = foundColliders[i].gameObject;
 
                 // Continue if the current collider go is the root reference
-                if (ReferenceEquals(currentColliderGo, m_RootReference))
+                if (ReferenceEquals(currentColliderGo, m_AgentGameObject))
                 {
                     continue;
                 }
             for (int i = 0; i < numFound; i++)
             {
                 var currentColliderGo = foundColliders[i].gameObject;
-                if (!ReferenceEquals(currentColliderGo, m_RootReference))
+                if (!ReferenceEquals(currentColliderGo, m_AgentGameObject))
                 {
                     detectedAction.Invoke(currentColliderGo, cellIndex);
                 }

com.unity.ml-agents/Tests/Runtime/Sensor/BoxOverlapCheckerTests.cs

             bool rotateWithAgent,
             LayerMask colliderMask,
             GameObject centerObject,
-            GameObject rootReference,
+            GameObject agentGameObject,
             string[] detectableTags,
             int initialColliderBufferSize,
             int maxColliderBufferSize
                 rotateWithAgent,
                 colliderMask,
                 centerObject,
-                rootReference,
+                agentGameObject,
                 detectableTags,
                 initialColliderBufferSize,
                 maxColliderBufferSize)
             int gridSizeZ = 10,
             bool rotateWithAgent = true,
             GameObject centerObject = null,
-            GameObject rootReference = null,
+            GameObject agentGameObject = null,
             string[] detectableTags = null,
             int initialColliderBufferSize = 4,
             int maxColliderBufferSize = 500)
                 rotateWithAgent,
                 LayerMask.GetMask("Default"),
                 centerObject,
-                rootReference,
+                agentGameObject,
                 detectableTags,
                 initialColliderBufferSize,
                 maxColliderBufferSize);
         {
             var testGo = new GameObject("test");
             testGo.transform.position = Vector3.zero;
-            var boxOverlapSquare = TestBoxOverlapChecker.CreateChecker(gridSizeX: 10, gridSizeZ: 10, rotateWithAgent: false, rootReference: testGo);
+            var boxOverlapSquare = TestBoxOverlapChecker.CreateChecker(gridSizeX: 10, gridSizeZ: 10, rotateWithAgent: false, agentGameObject: testGo);
 
             var localPos = boxOverlapSquare.CellLocalPositions;
             Assert.AreEqual(new Vector3(-4.5f, 0, -4.5f), localPos[0]);
 
             var testGo2 = new GameObject("test");
             testGo2.transform.position = new Vector3(3.5f, 8f, 17f); // random, should have no effect on local positions
-            var boxOverlapRect = TestBoxOverlapChecker.CreateChecker(gridSizeX: 5, gridSizeZ: 15, rotateWithAgent: true, rootReference: testGo);
+            var boxOverlapRect = TestBoxOverlapChecker.CreateChecker(gridSizeX: 5, gridSizeZ: 15, rotateWithAgent: true, agentGameObject: testGo);
 
             localPos = boxOverlapRect.CellLocalPositions;
             Assert.AreEqual(new Vector3(-2f, 0, -7f), localPos[0]);
             var testGo = new GameObject("test");
             var position = new Vector3(3.5f, 8f, 17f);
             testGo.transform.position = position;
-            var boxOverlap = TestBoxOverlapChecker.CreateChecker(gridSizeX: 10, gridSizeZ: 10, rotateWithAgent: false, rootReference: testGo, centerObject: testGo);
+            var boxOverlap = TestBoxOverlapChecker.CreateChecker(gridSizeX: 10, gridSizeZ: 10, rotateWithAgent: false, agentGameObject: testGo, centerObject: testGo);
 
             Assert.AreEqual(new Vector3(-4.5f, 0, -4.5f) + position, boxOverlap.GetCellGlobalPosition(0));
             Assert.AreEqual(new Vector3(-4.5f, 0, 4.5f) + position, boxOverlap.GetCellGlobalPosition(9));
             var testGo = new GameObject("test");
             var position = new Vector3(15f, 6f, 13f);
             testGo.transform.position = position;
-            var boxOverlap = TestBoxOverlapChecker.CreateChecker(gridSizeX: 5, gridSizeZ: 15, rotateWithAgent: true, rootReference: testGo, centerObject: testGo);
+            var boxOverlap = TestBoxOverlapChecker.CreateChecker(gridSizeX: 5, gridSizeZ: 15, rotateWithAgent: true, agentGameObject: testGo, centerObject: testGo);
 
             Assert.AreEqual(new Vector3(-2f, 0, -7f) + position, boxOverlap.GetCellGlobalPosition(0));
             Assert.AreEqual(new Vector3(-2f, 0, 7f) + position, boxOverlap.GetCellGlobalPosition(14));
             var testGo = new GameObject("test");
             testGo.transform.position = Vector3.zero;
             testObjects.Add(testGo);
-            var boxOverlap = TestBoxOverlapChecker.CreateChecker(rootReference: testGo, centerObject: testGo, initialColliderBufferSize: 2, maxColliderBufferSize: 5);
+            var boxOverlap = TestBoxOverlapChecker.CreateChecker(agentGameObject: testGo, centerObject: testGo, initialColliderBufferSize: 2, maxColliderBufferSize: 5);
             boxOverlap.Update();
             Assert.AreEqual(2, boxOverlap.ColliderBuffer.Length);
 
                 cellScaleZ: 10f,
                 gridSizeX: 2,
                 gridSizeZ: 2,
-                rootReference: testGo,
+                agentGameObject: testGo,
                 centerObject: testGo,
                 detectableTags: new [] { tag1 });
             var helper = new VerifyParseCollidersHelper();
                 cellScaleZ: 10f,
                 gridSizeX: 2,
                 gridSizeZ: 2,
-                rootReference: testGo,
+                agentGameObject: testGo,
                 centerObject: testGo,
                 detectableTags: new [] { tag1 });
             var helper = new VerifyParseCollidersHelper();