China did not make any specifics about Ukraine, Donbass and Crimean, did it? China said "firmly support Russia's core interest". So if Russia tells the west that "annexing" Crimea and controlling Donbass are part of its core interest, then China does pledge to support it, don't you think? Essentially both sides have given each other a blank cheque, it is more than what US has given to its allies.
I fail to see how you could taking out these specifics when China absolutely did not make.
In international diplomacy, word choices matter, not mental gymnastics to backwards justify your forgone conclusion.
"China firmly supports Russian national security interests or core interests" is a very different from saying "China formally recognized Crimean annexation and sovereignty belongs to Russia only."
This is basic diplomacy 101, China is speaking about broader NATO buildup threatening Russian sphere of influence, not about sovereignty of Crimea.
It's similar to concept of 'strategic ambiguity'. US uses this often over Taiwanese sovereignty, ambiguous and vague to not risk offending both sides while doing business as usual. China is intentionally 'strategically ambiguous' over Crimean sovereignty.