In my experience, it is temperature that is "allowed" to be higher when fermenting under pressure (pressure function is merely for ester and fusel/higher alcohols suppression - i.e., a cleaner fermentation profile at a higher temperature than would be the case at atmospheric pressure). It is the higher temperature that causes the quicker fermentation. Some also claim, however, that the aromatics are captured to a greater degree under pressure, especially if a closed loop transfer is then done to the serving vessel. Anecdotally, I would say that I ferment a bit quicker under pressure, but not hugely different. Then, again, I don't increase the temperature greatly. I would say that the hop aroma is a bit enhanced by the pressure ferment/closed loop transfer, but it could be confirmation bias, too.
Cheers!