The Fragment library has three different systems for doing view effects; Animation, Animator, and Transitions. Animations were first, then they were followed by Animators to address any short comings, and Transitions were built using Animators.

The new state manager introduced SpecialEffectsController which attempts to manage all of these effects and ensure their behavior is consistent. Where the old state manager started effects and kept going, the new state manager does things like waiting on entering effects to finish before moving to a Fragment to RESUMED and waiting on exiting effect to finish before destroying the Fragment's view.

With Animators and Transitions, this is all works wonderfully, but with Animations there are some issues. Unfortunately, there isn't much we can do to address these and therefore, we should handle Animations independent of the other effects and also hold them at a lower priority.

This has two main implications:

Animations will only be run if there are no Animators or Transitions present. This ensures we don't get any unexpected behavior from mixing systems and gives the other effects priority.
Entering Animations will not be part of the fragment lifecycle. So your fragment will not wait until an entering Animation is complete to move to RESUME.

Everything that you can do in an Animation should be applicable to an Animator as well. Whenever possible, you should always opt for using Animator over Animation.