Originally Posted by _kurt

Many (far from all) FAs enforce that the first class bin space is for F passengers only. For me, this is one of the most valuable benefits of domestic F. I can board late and still have a place for my bag.

You'll still get the odd flight where every F pax on a 738 has a rolling bag and then you're out of luck. This happens sometimes on flights with lots of international connections e.g. ex-MIA. But that has nothing to do with boarding groups. I would suggest that if the bag is compliant and the passenger is in F they should be allowed to board and try to find a place for their bag.