If it's not remote, where else could it be?

You are correct, but imagine to avoid people enquiring about if the position can be remote they write NO REMOTE instead of ONSITE.

Anyone searching through the comments for "REMOTE" is going to get all those NO REMOTE jobs as well, which is a pain. Using ONSITE makes it much more clear.

It's consistent with what people are posting and the directions given. From the very top:

> Please lead with the location of the position and include the keywords REMOTE, INTERNS and/or VISA when the corresponding sort of candidate is welcome. When remote work is not an option, please include ONSITE.

There's the possibility of (Remote, No onsite) in addition to (Remote, onsite)

I'd reduce that to 'REMOTE (?:ONLY)?'.