So the "No" argument is basically "she was never intended to be Robin long-term, therefore she's not"? Do I have that right? Because that's prioritizing the metatextual circumstances rather than the in-story ones, and I can't get on board with that. She served as Robin, therefore she's a Robin. It's really that simple.

To use a parallel, imagine saying that an Army private who got killed on their very first mission "wasn't really a soldier."