Disabling 'Predictive Text' seems to correct the bug; however, there must be something in the algorithm that's causing this that Apple does need to fix.
I begrudgingly accept autocorrect on iOS however. On a real computer, I turn that off too. I have learned since a long time ago that writing and editing should be two separate activities.
Possibly re-tuning of some LLM parameters? Or forgetting some bad learnings... sounds like it's specific to a small-ish percent of users.