Oh it's not just me?
Typing on my iPhone in the last few months (~6 months?) has been absolutely atrocious. I've tried disabling/enabling every combination of keyboard setting I can thinkj of, but the predictive text just randomly breaks or it just gives up and stops correcting anything at all.
I haven't watched the video, but clearly there's a broad problem with the iOS keyboard recently.
https://news.ycombinator.com/item?id=46232528 ("iPhone Typos? It's Not Just You - The iOS Keyboard is Broken")
It’s not just you, and it got bad on my work iPhone at the same time so I know it’s not failing hardware or some customization since I keep that quite vanilla.