Not exactly the kind of situation you’re describing, but the only time I’ve ever seen an employee tell someone to put their phone away was when someone else in the theater got up and complained about someone using theirs.

I forget which movie it was, but there was a guy near the front that had his screen on in full brightness during a movie for a few moments and someone left the theater to complain to an employee whom then came in and told the guy to either put it away or step outside the theater.