I think China needs to develop faster vertical troop transport capability. If this is a tiltrotor like the V-280 Valor or something different remains to be seen. In the late 1960s early 1970s a lot of countries experimented with VTOL aircraft. Most of these projects failed because back then avionics were not sophisticated enough or the designs were too expensive. One example is the Dornier Do 31.
China having something which can traverse the straights quickly and unload troops would increase the amount of possible options. By achieving early surprise it might be possible to capture port facilities early in the conflict and speed up the landing of heavy armored forces and supplies.
The difference between a Z-20 and a V-280 type aircraft for most of the PLA's missions (whether Taiwan or westpac as a whole) is not that decisive. Helicopter air assaults aren't that worthwhile and too high risk (same for paratrooper drops as well), for the strategic priorities China has.
If anything, the most useful of a V-280 type aircraft would be if it could be converted to an ASW helicopter, rather than as a transport aircraft.