Desktop Environment docs do not mention COSMIC Epoch
It appears that the COSMIC Desktop is now the default, but not only does https://support.system76.com/ still say "Pop!_OS Comes with GNOME by default," but the https://support.system76.com/articles/desktop-environment doc says the same thing and even worse, it doesn't mention COSMIC at all.
COSMIC is not default until Pop!_OS 24.04 is released (it is currently Alpha).
Weird, then I don't know why my coworker thought his new System76 laptop came with that by default (I personally don't have that laptop, so just heard about it)...
Either way, I think the Desktop Environment (Change) documentation should mention how to switch to COSMIC.
The confusion likely stems from the project formerly known as COSMIC, which is a collection of Gnome extensions that modified the behavior to a workflow we liked. Further down the line, we decided that the workflow we wanted was better achieved by making our own DE, rather than trying to extensionify Gnome into something it wasn't really designed to be. The new DE inherited the name COSMIC and is known as COSMIC DE.
To disambiguate, I usually refer to the old Gnome-based COSMIC as Gnosmic. But this is not an official nickname. It's just something silly I like to say that still gets the point across quickly.