Ah, well you see, China doesn’t have a casus belli to claim all of Russia. Of course, they might have deployed their foreign minister over to Fabricate Claims, but if so, they haven’t had much success with it. The most they could take right now is a duchy or a county, and it’s just not worth the Prestige penalty, or the costs of keeping their levies raised long enough to get their Warscore to 100%.