I am not too surprised China abstained. Doesn't it often abstain in situations like this anyways? I think they abstained when it came to Syria if I remember correctly.
This was their usual position in the 90s when they were much weaker.
They are a much bigger player now and they could have wielded that power likely without much consequence by voting one way or another, so their abstention is interesting but it makes a lot of sense. With the Russian veto, their veto would have been overkill other than to send a signal that Russia is not alone.
By abstaining, they give the west their moral victory, without really changing their position. I also probably think they have an interest against the kind of games Russia is playing with the west because of Tibet and Xinjiang