Ha yes, I’ve seen reports of this. Same with Buckingham palace.
On the Outside Xbox stream they were saying this is because the AI looks at the size of building and its location (e.g. residential, commercial, industrial), and then assigns it a suitable building type. For Edinburgh castle it sees a big building in a commercial district and presumes office block. It’s an interesting insight into how their AI works.
I think a big area of monetization for this game is going to selling the hand created cities and buildings, which will be much more accurate. I think if you’re using the base version you might have to put up with these weird autistic guesses.