I'm surprised by the people here who think this is some way unique to Apple. I'm 99% sure Gboard on Android does the same thing. It seems to be implemented differently and to be a bit more responsive to learning my behavior over time, but I've highly suspected it's been there for years. And I'm surprised no one has noticed this until now?

I'd have tried to work out more detailed behavior but I'm poor enough at swiping (at least with Gboard) that there's little point in trying to pin it down that well, at least for me.