Still an issue in 1.20.32 I've run into it a few times on my realm.
It happens with a 1x1 waterfall with only the top being a source block of water. It happens on 4th gen iPod and iPhone. What else I don't know.
yeah. the strait down flowing water is way to strong. you move up the water at 2 pixels per second at fastest.
This issue persists despite being set to resolved.