I am their target customer (I recently bought a very similar machine to these from Boxx), and I have no idea what Pop!_OS is. I can guess, based on the 18.something LTS that it's a Ubuntu derivative, but I don't know what that involves.
I'm pretty sure it's an add-on repo to Ubuntu which contains customisation of GNOME Shell and some System76-specific firmware stuff. (I have a System76 desktop from a few years back, but haven't run Ubuntu or System76's custom repo for some time on it, so I'm not 100% certain.)
Yeah, as far as I can tell, that's what it seems to be. But there's some breathless hype stuff about it that's obfuscating stuff on their site even though I'm their target audience.
