How do you know that? Have you been there and know the social situation there?
I hear China grants a lot of rights to their minorities, and allow them to have more children. Of course this is just what I've read.
This isn't new to China though tbh. China tried this occasionally in its history with its southwestern minorities (Miao, Yao, Zhuang, Yi, etc...). At many times, they tried it and explicitly banned it when rebellions/riots broke out. Nothing new at all in Chinese history. In those days it was through "mandates" and "decrees". The emperor would literally ban interracial marriage because it caused chaos. Of course the official narrative through the CCP is that there was economic and class oppression. But we all know the truth. As soon as you start taking women from another race of men, problems begin. It might not happen immediately, but its like a powder keg. Anything can set it off.
If what you are saying is true, I would suspect there to be riots nonstop in Tibet but that doesn't seem to be the case.
What you've said might apply to Xinjiang but then again I don't know as I've never been there. Just completely speculating.
Tibetans are far more attractive than Chinese subhumans
Tibetans don't look all that different tbh. Tibetans are literally the western branch of the Sino-Tibetan language family. Meaning very recently, Han Chinese and Tibetans were one tribe before they split off in different directions and became their own tribes.
Since their split, they have mixed with other tribes nearby. Today, Tibetans have a lot of haplogroup D3 (Very common in Burma). So Tibetans have a lot of Burmese influence and genetic admixture. And the Han Chinese (who went eastwards and southwards) mixed with other tribes as they expanded.
But in general the Y-DNA Sino-Tibetan marker is haplogroup O3e. Its the defining marker for both Tibetans and Han Chinese.