Yep, I'm also having more mistakes when typing. I've noticed it since iOS 13 or so. Probably something in the keyboard software has changed.
Basically, keyboard has a dictionary and predicts what you are about to type and which button you are about to press. It also makes some letters smaller and others larger, so there's more chance of pressing the right one. Probably some changes in software triggered the result we have now. Maybe there are too many words in a dictionary or something like that?
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This is a good example from the Apple's guided tour. Because there's no common word spelled "timr" or "timw", an iPhone makes a larger target zone for the letter E and shrinks the area for the letters W and R.