China begins with a whole network of remote island outposts, and, in case of a wider pacific conflict, is almost bound to do some sort of that Japanese did back in 1941. It's forced by geography.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.
In this sense, longer-ranged, faster (turboprop-level-fast), efficiently cruising rotorcraft is essential, and not having one(when opponent has one) by itself is a major, strategic disadvantage.
Furthermore, much like with longer-legged&fast amphibious craft - tiltrotors not just stretch defenders' reaction times, they expose much more of the actual Taiwan coastline to the risk of assault. Helicopter-proofing western coast is one thing. Helicopter-proofing eastern coast at the same time is a horror.