UK air is very complicated, so a Rotax cannot possibly run without a fuel return line. Everybody knows that!
Broad grin! Things get really funny though when almost the exact same comment could be read on several German forums... but worded in Teutonic, of course, which makes it only more picturesque.
So perhaps BE is just a tiny corridor of "normal" air between those two major imperfections? Or perhaps it is an outlier from France, where many things seem to be more relaxed.
Seriously though: on a high-winger, does it mean there is sufficient pressure available to push the fuel back up into the wing tanks? That requires some believing - or is THAT perhaps the reason one sees those big vent pipes on the S6 fuel caps? To create a bit of vacuum to assist in sucking the fuel up?