If I go into my iCloud account and remove the device off my list, does activation go away even if I didn’t explicitly remove it before I get rid of it?
If yes, that would be more than enough at this point.
Yes. It's possible that the device still "thinks" it's locked, but then the person who has it can factory-erase it, and when it contacts the server it will not show up as locked because you removed it from your account.