I'm 100% remote. I live in VA, and the company I'm contracted to is based in OH. So my chances of dropping in ad hoc are precisely 0%. I imagine most 100% remote workers would be in the same boat.
So the rule of "if you drop in more than 4 times ad hoc in a two month period, not counting major company events" works to separate you from a non-true 100% remote person.
Many Meta employees are “remote” but live in the same city as an office (I think it’s over half).
And that's a side effect of the pandemic, not because Meta actually wanted them to be remote.