It isn't blocked on the Steam store, but it's blocked on Epic. Curiouser and curiouser.
Thanks a lot for confirming this, and to ChrisSZ and ysbird as well.
I'm afraid I made a mistake with the EGS link, though - the EGS link I posted has the German language code "de" in the URL (I just grabbed the first link I could find and it defaulted to Germany for me). So maybe the EGS blocked you because of that - not sure how the region lock system works on that store (should be IP based regardless of which language you choose, right?)
Unfortunately, this is not the first case of a game being region locked in China
on GOG but being available on Steam. You can find more examples on the list
- these also include at least one game which is region locked for a bunch of other countries such as Taiwan or Malaysia.
Can someone tell me whether the Steam entry for Eastward mentions a different publisher? On GOG, it's Chucklefish.