> effectively abusing autistic kids results in a long-term, sustained, massive reduction in their autism symptoms?

While I'm dubious about this specific case, the basic dynamic you're describing there is the core controversy around ABA "therapy", which is effectively conditioning autistic children to act "normal" [1], sometimes through social pressure, sometimes through physical punishment that rises to a level legally recognized as torture [2]. It generally results in immediate behavioral changes, but also results in long-term PTSD [2].

[1]: https://whyy.org/segments/how-a-therapy-once-seen-as-a-victo...

[2]: https://en.wikipedia.org/wiki/Judge_Rotenberg_Center#Condemn...

[3]: https://www.academia.edu/35842784/Evidence_of_increased_PTSD...