I couldn't find any reference to it being blocked except in that article.

A test seems to show it's not blocked though:

https://viewdns.info/chinesefirewall/?domain=sci-hub.tw

Closest mention outside of original article is this The Verge article (2018), saying that they blocked China and Iran for a while because of too many requests from users; but this is sci-hub blocking not China banning

https://www.theverge.com/2018/2/8/16985666/alexandra-elbakya...