>You're the person they're trying to fool, so if they cheat successfully you would never know. You've never seen overt displays of bad cheating, which is different.

I don't think it's widespread at least, since in my experience people that do well in technical zoom interviews do not drastically decrease in apparent competence when we move to in person rounds.

People definitely get told interview questions by recruiters though, if you count that as cheating then it is everywhere.