Why does google state that animations should be disabled for UI testing?

To avoid flakiness, we highly recommend that you turn off system animations on the virtual or physical devices used for testing.

https://developer.android.com/training/testing/espresso/setup

I do remember that a couple of years ago animations were indeed a problem for my espresso tests. But recently I didn't see any errors introduced because of it.

Does somebody have insight why the stability regards animations has improved but why google is still recommends to disable?