How to reproduce:
1. Open the attached "1263490_AnimatorCullCompletely.zip" project
2. Open the "SampleScene" Scene
3. Select the "Animator" GameObject in the Hierarchy window
4. Enter Play Mode
5. Press the Space bar once to enable the Animator Component
6. Observe the Game view

Expected result: The "Animator" GameObject is animated when the Animator Component is re-enabled during Play Mode with Culling Mode set to "Cull Completely"
Actual result: The "Animator" GameObject is not animated when the Animator Component is re-enabled during Play Mode with Culling Mode set to "Cull Completely"

Reproducible with: 2018.4.26f1, 2019.4.7f1, 2020.1.1f1, 2020.2.0a20

Note:
- If the Animator Component's Culling Mode is set to either "Animate Always" or "Cull Update Transforms" and the Animator Component is enabled during Play Mode, the "Animator" GameObject will be animated
- If the Animator Component is not disabled before entering Play Mode, the "Animator" GameObject will be animated even with Culling Mode set to "Cull Completely"