I've seen plenty of rif-raf in the 1st at both ends on the 700s (and other stock and other TOCs for that matter) who clearly aren't 1st passengers, saw a group the other day in 1st on a southern 377.
Thing is I rarely see RPIs doing a sweep on Southern DOO, and I don't think I've ever seen one on TL. So they're just going to keep doing it I guess, or even worse not have a ticket at all.
On your side note, yes the REPs were a beast, they weren't normally allowed to run with no TCs, but I remember once or twice in the 80s coming up from BMH on one solo due to stock shortage. That certainly shifted some!