Probably because somebody competent in the Japanese military pointed out to him that all the 055s, carriers, LPDs and LHDs would be of limited use in a Taiwan scenario, but would be perfect to island hop all the way up to the Japanese home islands.
Chinese military strategists are not idiots and are not afraid of dreaming big.
If they are expecting direct US military intervention in Taiwan, then they will also be expecting Japan and Australia to tag along.
In the event of a decisive Chinese victory, with the US Pacific fleets, along with the Japanese and Australian fleets erased from the world’s oceans, it would offer China a perfect opportunity to obliterate the second island chain via direct invasion.
I doubt China would want to invade the Japanese home islands or Red Dawn Australia, but China will be well within its rights to take Okinawa and all surrounding islands on the basis that those islands were once again used by the Japanese to launch a war of aggression against China, so they will never be allowed to be used in such a way again.