Probably for the same reason that Italy doesn't have a communist or democratic route. It seems like the devs intended for china to be its own proper theatre of war, with its own major alliance blocks. In this case, the national front versus the co-prosperity sphere. It seems to me that, as a whole, ideology is a lot less emphasized for chinese nations in-game, and more emphasis on asymmetrical warfare, political jockeying, and realpolitik. The foreign aid tree is pretty good at representing that, and I think it's a shame that the warlords don't have access to it.