What’s the benefit of this conflict for China?
You are not asking the right question here or you are applying a very narrow range of pre-defined results.
Was there any benefit for PRC to start ussuri when it did with the USSR?...sustain it as it did and then have it ended as it did (Brezhnev literally implying he would nuke Beijing with mao inside if it came to it).
Or invade and get its butt kicked by Vietnam in 79?
PRC is not some calculative cost-benefit ratio monolith....there is plenty of buffer for them to do lab experiment on all size and manner of countries....especially if there is little to no blowback on their core spine.