On one hand I think that if a fanfic has a big enough recursive fandom to support an exchange scene based off of it and it alone, and is very clearly different from the source canon, then it's at least as valid as the "What if" stuff.

On the other hand if that was my introduction to recursive fandoms I sure as heck would not think it was even remotely valid. That has to be the worst evidence post for that sort of thing I've ever seen. They don't even name the actual fandom, wtf.