The company I work for allows pax to use phones while refuelling, but the nearest part of the grounded refuel rig is about 10m from the nearest pax and the other side of a pretty effective Faraday cage. Pax are not supposed to use phones on the ramp, tho no one bothers to stop them nowadays.
Whislt refuelling my C150 I was amazed to see the chap using a walkie-talkie clamped to the nozzle with the same hand! I told him to stop, pretty sharpish, and he claimed, vey huffly, that he'd never heard of any danger in fifteen years of refuelling!
Power output of a mobile phone is no more than several milliwatts, I doubt one could induce a spark if you tried in a laboratory. It does surprise sometimes that presumably technically trained people on this forum swallow such obvious hokum.
Cooking popcorn and eggs indeed! Heard the one about the moon and cream cheese?