I don't think I would put terriers or pugs in that category... The difference between what people call "hypoallergenic" ot not, is if they have hair, or fur. Some breeds like the shih tzu, bichon, poodle. ect, have hair that grows contstantly, like ours. Other breeds have fur, one hair grows, another grows under it and pushes the first one out, i.e. they shed.. It is a myth.. It is fantastic that people find breeds that don't bother them but I think that these breeds should just be classified as sheeding and non shedding, leaving the allergenic out. The common allergen is dander, a protein in the animals slaiva, that when dried becomes airborne, and breathed in. Therefore hairless dogs, like the chinese crested, and xolo(don't wanna spell the rest but it sounds like showlowitzquintly, lol!) are not hypoallergenic either...
Some people are just having good luck finding breeds that they can live with and I think it is just luck. There are also people that do not have allergies but use it as an excuse to not look evil when they want to give up their dog. Otherwise there could just be something else they are allergic too. Either way it is not fair to classify any breed as being non allergenic, because they can still cause reactions.