Tibet was struggling to gain any sort of international recognition and was, as you say, independent de facto and not de jure. They were about as independent as the Principality of Sealand. In 1906 Great Britain and China signed the Convention Between Great Britain and China Respecting Tibet, which recognized China's sovereignty over the region. The brief period during which the de facto independence existed was during the Chinese civil war, when the Tibetans took advantage of that situation and agitated for independence. Nothing ever became of that effort, because the formation of a new state requires international recognition.
The list of treaties recognizing China's authority over Tibet goes on, whereas there exists a distinct lack of anything resembling international recognition for the existence of an independent Tibet.
So that's why I have the idea that Tibet is a province, subordinate to the central Chinese government.
Also, being an independent kingdom with antiquity Tibet has a right to challenge status quo based on history, which again is nothing like Utah/Mormons and the US since there was no Mormom state prior to it being a US territory.
Edit: To give you some perspective, here is a gif showing all the Chinese empires since the Warring states (350 BC).
https://en.wikipedia.org/wiki/History_of_China#/media/File:T...
The only two periods (from 350 BC to current) under which Tibet came under the Chinese empires was
Yuan Empire (1294 - 1368)
Qing Empire (1644 - 1912)
Finally annexation by the communist party in 1951.
It must be noted that both the Yuan and Qing empires were non-Han (Mongol, Manchu respectively).