[cheebacheeba]

Most people have allergies not to the hair but the saliva of cats, being as it is they're licking themselves clean all day etc, it mixes in with the oils on the tips of the fur as I understand it...so they walk around moving their spit onto people.
My GUESS is that the saliva is not any different in these cats, just that it's less portable and they don't leave it everywhere on the shedded hair that they don't have. Not sure if they groom the same way or not, but I'd assume since they get dry skin the saliva isn't going to be as much of a problem to those with allergies to it, it probably dries off pretty quickly.
If it's just that they don't have hair...you probably could...theoretically...shave any other cat, if you were so inclined.

That said this is purely conjecture on the basis of what I know about "cat allergies" and what the usual problem is.