I have a few stories to tell about this. I teach at a university in the US (I have former doctoral students who are now faculty at Chinese and Taiwanese universities). In addition, quite a few years ago I became close friends with a Chinese coach who later went back to China, where he continued to coach TT. (Some day I will relate the kind of sad story about this guy's experience in the US).
Not too long after he went back to China, I went to China to give some talks on my research at Chinese universities (in Wuhan, Beijin and Hefei). In Wuhan I met up with my friend, and we spent several days playing, which was a blast. We actually played at several places, each one of which was amazing in terms of playing conditions. One place he took me was a table tennis school (kids started there when they were about ten years old, and lived at the school). I played several of these kids (12-14 year olds) and was routinely annihilated without mercy. I met a couple of coaches (got a free lesson), got a feeling for how the kids spent their days. They played a lot of TT each day, obviously, but my impression is that other aspects of their education were not neglected up until they reached a certain age, around 14 or so, when the TT became a lot more emphasized. For example, some of the kids could speak a bit of English. I never could figure out what the older kids ended up doing if they didn't make city or provincial teams (and most of them probably didn't, if for the simple fact that there were too many of them).
In addition to that experience, a few years later I learned that one of my Chinese students here in the US had attended a TT school in another place but had stopped when he was 14 because his parents realized that while he might make the provincial team where he came from (because it was one of the weakest in China) but that beyond that he would have no real future except as a coach. So he transferred to regular schools, worked hard, and eventually was able to come to study at my university in the US (as an undergraduate, which is a bit unusual, it is more common for Chinese students to come here for graduate programs, but his parents have quite a bit of money I think). He ended up getting a MS degree in engineering, got married, got a green card, has nice job here now and will not be going back. But he told me quite a bit about what his life was like at the TT school because we used to play fairly regularly for a couple of years. Later he just stopped playing. I suspect he mainly played with me out of friendship but didn't actually enjoy TT so much.
I have a pretty good understanding of the rigor of top level Chinese universities, but ALSO how the Chinese government keeps a close eye on their universities (and the faculty) and at the end of the day the top Party official makes many key decisions, which would include making sure that some of their favorite people are awarded degrees. So those experiences inform my opinions about a lot of what I see in this thread.