Yeh, Trents is a RWD hub dyno, still he shouldn't need to justify his figures, it is on par with most of the other local tuners machines, but obviously dispenses with the wheelspin and over strapping required at that sort of power.
If you ran it on a roller I would expect to see minimal losses, although I still haven't been on Trents to compare my figures. As you say though, same dyno same day, or take them to the drags together is the only way to know.