Yes, the anti-rollover spill valve is different. If your car happened to flip over this would keep the gasoline from spilling out the fill spout.
The vapor valve is what allows gasoline vapors to escape the tank. These then run through vacuum hoses to someplace under the hood where they are fed into the engine to be burned. The theory would be that something keeps the vapors from escaping and the pressure shuts off the fuel dispenser. Its not really possible to give that mechanic more ideas beyond that because we don’t know what was already checked. The question would be whether or not the mechanic check out any other parts of the evaporation system.
I think the rollover valve is a more likely problem.