I feel like a single line through would have been the correct design choice, still, because in practically every other context, that’s what’s used (no smoking signs, for example).

Seems like many, many other places around the world put a line through for road signs (though a couple outside Europe don’t, and even some inside Europe do): https://en.m.wikipedia.org/wiki/Prohibitory_traffic_sign

My 2¢, Europe is wrong on this one, despite being right on so much else haha