Lets say you have an api bug where you are allowing clients to ask for data with a very expensive query, and you want to dissallow that behavior. I think it makes more sense to change both the api spec (remove the endpoint) and the backend (dissallow queries of that kind in the future) in one go. That way you can note in the one PR exactly why both changes are made, referencing whatever bug/postmortem. Making two PRs that separately look like fixes to the issue can be confusing later, and don't really buy you any clarity in the PR itself.

Is it possible to break them up? Sure. Is it better to do so? I don't think so.

Also, for clarity, neither myself, nor op, every said couldn't be done.