Steps to reproduce:
1. Download and open the attached project
2. Look at the hierarchy or project windows and see different hierarchy

Expected result: Character_rig@anim should have the same removed (optimised) hierarchy as Character_rig
Actual result: Character_rig@anim has the old hierarchy without "Optimize Game Object"

Steps to reproduce from scratch:
1. Open any modeling program(i.e. blender)
2. Create a model
3. Create another model
4. Parent it under the first
5. Create an animation for the parent model
6. Export as FBX
7. Import it into Unity
8. Duplicate it
9. On the first model, in the Rig settings in the inspector window, check "Optimize game Object"
10. On the duplicated set Avatar Definition as "Copy from other Avatar"
11. Set the source to the original model's avatar
12. Click apply

Result: the second rig will not retain the "Optimize game Object" optimizations

Reproduced on 5.2.3f1. 5.3.6p8, 5.4.0f3, 5.4.2p3, 5.5.0b9, 5.6.0a2 (e9ba82db0b63)