Steps to repro:

1. Open attached project and '11_AutomaticInstancingSorting' scene;
2. Enter Play mode;
3. Open Frame Debugger (Window -> Frame Debugger);
4. Click Enable button;
5. Expand draws under Drawing -> RenderForward.RenderLoopJob section;
6. Scroll down and find 2 last calls for Draw Mesh (instanced) Sphere 2(Clone);
7. Click on the last Draw Mesh (instanced) Sphere 2(Clone) call;
8. Observe batch breaking reason in 'Why this draw call can't be batched with the previous one' section of FD window.

Expected result:
The batch is broken because instanced batch for Sphere 2 gameobject has overflown its maximum number of 500 instances. Corresponding message should be shown in FrameDebugger window.

Actual result:
The message: 'Rendering different meshes or submeshes with GPU instancing' is shown. This message is inconsistent with user expectations (seeing why instanced batch has actually been broken).
See attached screenshot.

Notes:
- Reproducible on Windows 10 and OSX 10.12.5;
- Reproducible in 2017.2.0a1, 2017.1.0b8, 5.6.1p2;
- Reproducible in both Editor and Standalone player.