I think the real reason for them warning to not use your cell phone while pumping gas is that it's a dangerous distraction.
Pumping gas into your vehicle may seem mundane, but in fact there are real hazards if you do the wrong thing, and paying attention to a cell phone is a great way to do the wrong thing with the pump.
Does anyone remember the Samsung Note 7?
No, the signs are there regarding radio-induced sparks.
Some British science show did everything they could to cause such a condition. Didn’t work. Ll
What is more dangerous is sitting in the car while fueling, then getting back out. During cold dry conditions, for those of you who live in areas where there is real winter, it is easy to build a static charge which can be an ignition source.
Years ago, the San Antonio Fire Department did a demonstration for KSAT television news on an unusually cold day where a fireman caused a static discharge near the filler inlet while fueling. Vapors ignited. If left alone, the vapors will eventually extinguish. What some people do however is remove the filler nozzle - when gasoline is still flowing - and things can go very wrong quickly. If you absolutely have to go back in the car when fueling (not recommended, regardless of how cold it is), touch metal after you get out of the car, but still some distance from the filler in order to discharge any static electricity.