The ZTQ-15s are light, meaning that you can stuff more ZTQ-15s to do an amphibious landing or amphibious reinforcement than you could with ZTZ-99As.
The Type 10 is actually 40 tons with its modular armor removed and 44 tons in standard configuration. You get the feeling the Japanese are thinking the same thing; lightweight Type 10s can be deployed onto islands by amphibious lander more efficiently than Japanese Type 90s. The ZTQ-15, likewise, is supposed to be around half the weight of a ZTZ-99A, implying that you can stuff two ZTQ-15s for the same footprint as a ZTZ-99A.
Lighter weight and smaller size comes with versatility sure. But don't go drawing conclusions about Type 15 being designed to be deployed by ship to fight Japanese Type 10s. It's outgunned and probably can't penetrate Type 10's front armour. Japanese idea about up and down gradable MBT is similar sure but that's where the similarities end.