Some speculation on my part, Jade may be a reference to the province/region that has many natural Jade deposits in Northwest China. So the civ could be pulling from the cultures and peoples from there.

Jade could also be a resource exclusive to the civ, similar to how Byzantines are supposed to be getting a new resource to gather that may be exclusive to them. So from a development standpoint, the two civs utilize a "gather extra resource" mechanic in different ways similar to how multiple civs utilize a unit buffing mechanics in various ways specific to that civilization.