Thanks for the responses everyone.
Part of the reason why I was curious about this in the first place is due to the fact that all Falco's hub drive motors, regardless of the wattage rating, are all exactly the same price. I've noticed this with other brands as well, so it made me assume that they're all likely the same, and that the wattage is just being determined by some sort of setting or something.
I know that it's safe to use a 48v battery with the 500w Falco motor, as kit can be ordered with either battery, and their literature states that it will work with either voltage. My question is just whether it will produce more power or not. Because it would certainly be possible to build a motor contained two separate sets of windings, one for each voltage level. Both this or some other type of limiting device could easily cause the motor to operate at 500w, regardless of what voltage you supplied it with.
So I guess that's more precisely what my question is. Because in the absence of those two possible limiting factors I mentioned, that means my 500w motor hasn't been producing 500w all this time with the 36v battery I've been using. But that would be odd though too, because the 36v battery is the standard battery that's offered with the 500w kit.
And yeah, I know heat is an issue. I've been wondering for a long time why they don't manufacture these hub drives with cooling fins. It would add only a trivial amount of both weight and friction.