Some do, some don't. Rather than hold up the flight try to identify which are which on a passenger flight (and sort out the ensuing arguments from disgruntled pax), a blanket ban does the job.
For one example of interference caused by an electronic device, I used to fly a helicopter type where a live mobile phone being "polled" in flight would bring on the aft baggage bay smoke warning. Because there was no fire extinguisher in that bay, the warning coming on in flight meant an immediate landing. Not easy or safe over hostile terrain, in bad weather, or at night.
The anomaly was that the manufacturers said it shouldn't / didn't happen. That was probably because they hadn't carried out trials using the European phone frequencies, only those used in USA. Descending towards the sea at night, thinking the aircraft tail is going on fire, is no time to find these things out.