The point isn't really that I necessarily want to import the building, but that GRB is usually correct (as much as I hate government data). Also, I do map two adjacent houses as a single building, if it's a single building that has been split so that two families can live there (the case in which it would be in GRB as one building).

It's also a pragmatic thing: if I don't import it, sooner or later someone will, and they might not know what's being discussed here, so I'd rather map it in a future-proof way.