Yes, but that doesn't point to it not being a remodel either. It's only a tiny bit easier to do on tubes before they're built into a frame. Still quite do-able as a retrofit. In fact the "exit wounds" at the bottom of the downtube has to be done after the tube is in the BB shell, so that part is 100% the same whether original or retrofit.

The other possibility, that the frame was built this way to begin with, seems less likely, because the lugs, seatstay attachment, and long dropouts are all of a different era than the internal routing or the fork crown. Of course someone could have made a '72 style frame in '82, it just seems less likely.