United does that too, like everywhere.But they use stanchions to create cattle chutes. It's hilarious because in SF it seems like everyone is in group 1 or 2 and the lines will go block another gate quite a bit. On SFO/EWR flights I've seen group 2 have to check carry ons because the bins are already full.
except for the few poor souls who spend their every waking moment in the air/traveling for work, everyone flying delta is zone 1 too. especially after they reward people who agree to check their bags with zone 1 loading access. they have to do this because they charge for checking bags and their ohead bins fill up.
so what you end up with is a bunch of people who have no clue what they're doing, not being told what to do
and somehow in some people's minds, all of this is better than swa