A recent one was "your wheel is going round!"... I am on a bike. Wtf does that even mean? Like... That is how bikes work?

That's the prank.

The idea is that they "warn" you of something completely normal (like your wheel being round) and say it with a concerned tone (like how they'd say "hey your tyre is flat!") so that you'd naturally stop your bike to check, making you look like a fool for stopping to check that your wheel is round.