Turns out the material immediate set doesn't really work.

ScriptableRenderPipeline/LightweightPipeline/LWRP/Passes/ForwardLitPass.cs

 
             if (cameraData.msaaSamples > 1)
             {
-                m_DepthCopyMaterial.SetFloat(m_SampleCountShaderHandle, cameraData.msaaSamples);
-                m_DepthCopyMaterial.EnableKeyword(k_MsaaDepthKeyword);
+                cmd.SetGlobalFloat(m_SampleCountShaderHandle, cameraData.msaaSamples);
+                cmd.EnableShaderKeyword(k_MsaaDepthKeyword);
-                m_DepthCopyMaterial.DisableKeyword(k_MsaaDepthKeyword);
+                cmd.DisableShaderKeyword(k_MsaaDepthKeyword);
-
-            m_DepthCopyMaterial.DisableKeyword(k_MsaaDepthKeyword);
         }
 
         void CopyColorSubpass(ref ScriptableRenderContext context, ref CameraData cameraData)