I’ve encountered several of these, but (at least on iOS 26.2), I can’t reproduce the typo one.

> Autocorrect Won't Take No For An Answer. You fixed it. It unfixed it. You fixed it again. It unfixed it again.

My experience is after the system makes the first autocorrection, the word is underlined, allowing me to revert to the original spelling. Then subsequent instances of the word aren't autocorrected.

It’s true though that if I leave the context and enter the same unrecognized term elsewhere, it’s the same grind. The only fix for this is to spotlight search for “Text Replacement” settings page to essentially add it to the iPhone’s dictionary. Clunky, but personally only have had to do this twice.