Alright, here's my understanding of the problem. While I have no experience whatsoever of aviation refuelling, and I may get reactions of "well duh!", I have grown up behind the till of a petrol station, and at least understand the theory of no phones allowed around refuelling of cars.
The problem is this: an empty fuel tank is full of fume-carrying air, so when the tank is opened and fuel starts pouring in, this air has to be ventilated. I don't know what you use to get the air out, whether there's a seperate vent for these fumes or if they come out the hole the nozzle is inserted, but either way you get these fumes that are highly flammable expelled at some point around the aircraft. That's why there's no smoking anywhere near any refuelling. not because of the actual fuel, but the fumes coming from it.
A small aside. We once had "neighbours" the other side opf the village, and these people one day, as you did in those days, decided to burn some newspapers. Coming out into the garden I smelt the burning, and fluttering in front of me as a charred peice of burning paper. My father saw it too, and immediately went to the police. Normally no one'd take a blind bit of notice, but had that gone the other side of the house, and fluttered over to someone filling petrol, WHOOOOOOM!
You can't allow anything to ignite those fumes, and that means paper burning, cigarettes, or the electrical circuitry of a mobile phone (which on some components can get very hot). I wasn't sure about how radio waves can/can't ignite fuel, but anything with electrical components has the potential to be a fire-starter. just one spark and it's lights up.
How's that? I hope I'm not stabbing in the dark here.