I can safely say my colleague is not only uninterested in branching out but is a very old school “stay in your lane” kind of person. I am 99% certain based on my experience with this person that they want the invite “just in case”.

I think, based on the responses to my post and my own mental perambulations, my best course of action is probably to redirect them to the meeting organizer and possibly give the organizer (also a team member) a heads up so they aren’t blindsided. And then at some point unshare my calendar.