Animations get skewed/distorted when animated objects are scaled and "Optimize Game Objects" is selected

How to reproduce:

1. Open new project and import package
2. Open the scene called "Scene"
3. Notice the monsters that are vertically aligned (Normal on top, optimized bottom) don't have the same scale, even though they have matching scales in the inspector.
4. Press play - monsters get scaled correctly
5. Notice strange skewing/rotation behaviour on optimized model

Workarounds:
1. Do not scale the animated object and any scaling would be done in the model
2. Disable "Optimize Game Objects"

Reproducible: 5.3.0f4, 5.3.1p1, 5.3.1p3
Not reproducible: 5.2.4f1