Steps to reproduce:
1. Open the attached project (CharacterInstancing (u5.6.0a2).zip)
2. Open the Assets/AnimationMatrixExtraction/AnimationMatrixAssetTestScene.unity scene
3. Run the scene (You should see 10,000 Lerpz characters rendering, arranged as a grid ( 100x100 ) on a plane. Each instance is unique, with its own color and frame animation. Due to size its hard to see any details, but switching to scene view fixes that)
4. Open the Frame Debugger
5. Start stepping through the drawMeshInstance calls
6. Upon reaching the 5th and 6th drawMeshInstance calls you should not see any change in the frame Debugger view

Expected result: DrawMeshInstanced should not render empty instances
Actual result: DrawMeshInstanced appears to renders empty instances

Note:
Bug relates to features introduced in 5.6.0
If you want to play with the number of instances rendered per DrawMeshInstance call, select the 'TestFramework Combine' gameObject and check the inspector, 'NumInstancesPerGroup' be set to 1000 (with 1000, 1020, 600, 400, 200, same behavior)

Reproduced with: 5.6.0a1, 5.6.0a6, 5.6.0b1