Animator hierarchy with its avatar root nested in the hierarchy (not the same as Animator transform) will show missing properties when opened in the Animation Window.

Going in playmode or previewing the animation in the animation window works fine however.

Repro:
- Open SampleScene.
- Open the AnimationWindow.
- In the scene, select Male_Gen1.
- See that properties appear normally in the Animation Window.
- Now, select Nested_Male_Gen1.
- See that properties appear as (Missing) in the Animation WIndow.