Doesn't make sense?
Drain all of the fuel out of your car petrol tank then drop a match down the filler cap and providing that there is also a bit of oxygen available, you will soon see why it makes sense.
Apples and oranges...
Jet-A has a flashpoint from +38C, gasoline/petrol from -43C.... which makes an enormous difference.
Cargolux is an approved DG carrier, and it is not the first time they shift helicopters. Something tells me they know the regs better than the average Pprune here. Accidents can occur though.
Different rules for passenger and cargo aircrafts...