An aspect of cultural politcs of chinese government
In Lhasa / Central Tibet there is one site of world heritage, the Potala Palace (including the Jokhang Temple Monastery) – http://whc.unesco.org/en/list/707. Both have no rating of the chinese tourisme authority (nore AAAAA neither AAAA). For example in Beijing the Great Wall and the Forbidden City have both signs: World Heritage and „AAAAA“. And in this context please look at one publicity of chinese governement you find all over Central Tibet. If your are interested in more information then I can send you the list of „AAAA“ and „AAAAA“ touristc sites.