Of course it's not China or the CCP torturing Uyghurs. Rather, it's individual Chinese prison guards (who may or may not be in the CCP or Uyghurs or both) torturing individual Chinese prisoners (who may or may not be in the CCP or Uyghurs or both).
The CCP leadership may intend prison to be places of transformation instilling a sense of gratefulness for the CCP's benevolent rule, thus requiring prisoners to be treated well, kept in good health, provided with a good education so they will be able to earn a living after release doing honest work rather than having to work as actors or whatever...
But that costs a lot to implement and who's going to implement it? Inexperienced prison guards who were just recently hired when the state increased it's security budget in Xinjiang and who didn't go to a police academy where they learn fancy stuff like "torturing people may make them rat out their friends and earn you a promotion for making your arrest quota, but in the long term it fuels resentment and destabilizes the country, so don't do it" since there aren't enough of those graduating each year, and you may recall that the whole reason re-education is even necessary is that the education system in Xinjiang failed to properly instill Socialist Values like patriotism and democracy and so on, so why would it have succeeded at instilling the idea that torture is bad?
Actually, even if they all had college degrees that wouldn't completely curb abuse, since driving children to suicide https://mp.weixin.qq.com/s/BRYqWk0GGaGZGkI1S9EGRg or torturing them with electric shocks https://zh.wikipedia.org/wiki/%E8%B1%AB%E7%AB%A0%E4%B9%A6%E9... is also illogical, yet presumably college-educated teachers still did it.