Is it surveillance pricing or is it just offering you a different fare class?

For example, the United "fare classes" decoded; https://i.imgur.com/mNZ3gYc.png

I suspect they're just shifting fare bucket availability dynamically. Less G (lowest discounted) fares, more U "high fare" economy tickets when someone searches on the fly.

Somewhere you'll be able to find a ticket counter to walk up to though and ask for that G-class economy ticket, though. Much like how I book my tickets on Breeze Airlines at the ticket counter on Tuesdays at 10 AM, to avoid the technology fees - and fly for something like $30 round-trip to DC and back.