china non first use was orginally meant for US/Soviet.
1. they have much less nuke compare to US/USSR
2. they don't think any countries will be stupid enough to use nuke. hence they keep minimal deterrance policy, keep warhead around few hundred and not building up nuke aresnal like US/USSR.
unless some country invade deep into china mainland i doubt they will use nuke at all. and the only country can do that might be US, and i doubt US want that at all. so yes china is not gonna use nuke in a conventional war, but they always keep a minimal deterrance 2nd strike capability.