I may be way off base here, but i keep thinking whether the loan includes funds for the renovations (and not just purchase of the building) might be relevant. On a smaller scale, for example, if a borrower gets a loan to buy an office building, then intends on his own to renovate it into a home (maybe with, maybe without a specific timetable), it would seem to me to possibly be a gray area. Perhaps in that scenario, the purpose of your loan would be to purchase an office building, period, whereas if the loan is also intended to fund the renovations, you would have a more concrete basis for calling it a dwelling for HMDA purposes.
As stated, i may be way off base here and i mention it only because i can't get it out of my head on this scenario.
I'm fixin' to fix that.