It makes political sense for China to appeal to solidarity with global south, but according to the historical definition of the term, a high income advanced economy making up a majority of global industrial and scientific advances essentially violates every criteria point, especially since China isn't even geographically south either.
Japan and SK are considered global north, and besides attitude to US, smaller size and having worse work life balance, there's nothing (development wise) that sets them apart from China.
Global south has for me always been an unclear term, as China would simply be global north if it had a positive attitude to US. The lack of clarity is by design, because the unclearness of the term means a large umbrella of potentially pro-China and anti-US can be gathered.
But that's basically the real job of "global south", the quiet part nobody says out loud is that it's nations that stand to benefit from and may assist in carving up the opposing US sphere.