Weird animation of UIModalPresentationPopover when keyboard is displayed

I'm working on an iPad app. The app displays a main menu via a UIModalPresentationPopover. The menu contains various text fields.

The popover's source rect is located towards the bottom right corner, such that the popover's little arrow points to the right. (This is important for some reason.)

When the keyboard becomes visible to edit some text, the popover does a curious animation as it slides up to get out of the way of the keyboard.

It instantly resizes itself to infinitesimally small when it starts sliding up, and then expands back to its original size as it's sliding up.

If I change the source rect of the popover such that the little popover arrow points down instead of to the side, it does not do this contract-then-expand animation.

The app did not do this when it was built for iOS 11 (or 12?) but is now doing it when built for iOS 13. I just checked by running my old source code and it does seem to be new-for-iOS-13 weirdness.

Does anybody have an explanation for this, or any idea for how to get it to stop doing this? Thanks in advance!
Can you file a bug report for this and attach a test case that reproduces the issue and at least include a screen recording of the issue. Please reply back with the feedback number.
Done. Feedback FB7843105.
Weird animation of UIModalPresentationPopover when keyboard is displayed
 
 
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