I suspect you’re right. It seems that more scopes get added as they are asked for. You could with a custom plugin if you’re self hosted. You could submit a PR and or post as a Feature request. If you’re an enterprise customer you could have your leadership ask. 
Hmm. Now I wonder about adding a custom api scope in a plugin is possible (especially having one plugin add an api scope for another plugin). I suspect that it is, but haven’t seen it done.
Maybe just create a user for just the api so at least you’d be able to track it that way.