Pilot on short-final screams 'turn off electronics'

I was recently on an American Eagle flight between Toronto and Chicago. On short final the pilot came over the speaker and in a flustered voice told us someone still had a phone on and that it was causing problems in the cockpit.

Upon landing the pilot said that if they had not had visual contact with the runway they would have had to go around. I asked upon existing and apparently, whatever was on stayed on.

After 1000s of flights I had never actually heard of a a device actually causing interference that mattered. Actually, my cousin, that is a commercial pilot, says he routinely keeps his phone on for whole flights.