How to remove react-transition-group animation delay on mount?

Question

css

Can you please tell me how to remove the react-transition-group animation delay when mounting?
I have a dropdown component that should have unmountOnExit, but there is an animation delay on entering when unmountOnExit is used, if not doing unmountOnExit, and set the animation values ​​to

const transitionStyles: any = {
  entering: { transform: 'translateY(0%)' },
  entered: { transform: 'translateY(0%)' },
  exiting: { transform: 'translateY(-100%)' },
  exited: { transform: 'translateY(-100%)' },
}

, then everything works fine. I first encountered an unexpected delay in the react-transition-group, in theory everything should work as it should.
Here is the source code with animation delay. I will be very grateful for the help
Link