I had actually totally forgot about that element in the book, but I also wasn't as deep into ML thought and Chinese history when I read it about two years ago.
Criticism of relativity and Einstein himself was a big theme in China, from the founding of the PRC all the way through Deng's reform period.
If I remember correctly these flashback moments in Three Body Problem take place during the Cultural Revolution, puts it right in the middle of this large cultural and academic debate over the theories of relativity.
I just read the abstract of this academic paper but you may be interested in making a Jstor account and skimming the whole paper.