My guess is that the 'wrong letter entered' bug is by design.

The keyboard animation happens on the touchdown event, whereas the letter is entered into the text box on the touchup event.

Between the two, more information might emerge about the touch - for example the exact shape of the touched area, and movement during the touch, etc.

I would guess the keyboard sees a down in one spot, and an up in a slightly different spot which falls into another letter.

I tested this, and if I have slide-to-type disabled, and slide my fingers, then every letter I slide over will highlight, but only the letter I let my finger up on will show up in the text input box.

If I don't have slide-to-type enabled, then only the letter I press down on will highlight, and what shows up in the text input box is pretty inconsistent for horizontally adjacent letters.

You can indeed see this behavior in action by tapping a letter and briefly swiping slightly to an adjacent letter. Maybe I’m missing something but I don’t see why the letter should be submitted on touch-up, since I’ve never intentionally tried to correct an individual letter between touch-down and touch-up.