Some can tell, some can't. this girl is the most famous Tibetan singer in China, Can you tell her from Han, Koreans and Japanese?
Alan Dawa Dolma - Wikipedia
en.wikipedia.org
And also as I mentioned, Tibet is a tourist hotspot in China, in some places tourists can easily overwhelm the local population, but they are not counted as the local population.
LOL love your way of twisting, since 1951 several generation of Han Chinese may be regarded "Tibetan" for you.
But Tibetans and Xinjian Uygurs have clear different facial / racial attributes than Han Chinese, if you can't differ you must be blind. Tell your stories to people who don't know China and never been there.