Not surprising. I've noticed other stations with TSA ID checkers doing nothing to enforce the line. There's usually a sign, but a lot of pax ignore it.

I overheard one guy trying to justify to his protesting companion why they were entitled to use the premium line. "Well, I'm sure I'm premium, anyway." (I could see a big ZONE 4 on his UA BP, too.) And I've seen others "rationalize" the line poaching with such stuff as, "I was an elite two years ago," etc. And the ID checkers just let them walk on by with nary a comment...

MIA was the last place I can recall the ID checker actually caring, and she wasn't TSA. LAX was OK last few times I was there, too, but it's been a while since I flew out of LAX and not another area airport.