Hi Doors I didn't dare try it. That the door actually moved at all was enough for me. Peugeot doors don't move a bit when filling is in process. If you say it stops before hitting then I'll take your word for it. Don't fancy trying to prove it much.
Just finished washing car by hand, (no water shortage).When I remembered a post regarding opening rear passenger nearside door when filler flap open, I discovered that there is indeed a "stop" that will not let door go too near flap. (normal door opening force used)
There must be child locks somewhere to stop your boys accidentally opening the doors. But even if they did they would be safe because of the seat belts. When you think of it accidentally opening a normal swing rear door would present far more of a hazard.