The rules about fueling with pax on board were written at a time when highly combustible Avgas was poured in through overwing fillers. The risk associated with pressure-refueling Jet A1 is much lower.
I may be too young in the business but is anybody aware of a refueling incident that might have posed a risk to pax if they had been seated with their belts fastened?
The current rules make sense but doing more would be overdoing ist. There are so many other things that could happen which would require an evacuation which are not covered by any security regs, so there's really no need to single out refueling for further attention.
Our company useses pretty much standard JAR-OPS procedures although two-way communication is hard to maintain in some types if they don't have a connector at the refueling panel.