The separation point is weird on the album. I recall it being more "correct" on LSFNY, and that's where I think of the split truly being. I think MP may have commented on that somewhere? Or maybe I'm remembering entirely wrong.
Being a concept album, the lines are a bit blurrier. I do consider it a song, it's just not a particularly useful song on its own, and one that is definitely dependent on FT, similar to Overture 1928 / SDV, or The Mirror / Lie, but to a much greater degree than either of those because there's no way it stands on its own unlike the rest.
I still don't think it was a bad idea to separate it as they did, because it acts as a bridging track, like a breather. Whether it's a song, or part of an act, or whatever they think of it as, isn't as relevant to me in the context of a concept album.
It's funny how different my opinion is here to the earlier discussion.