It can be because I'm not particularly huge on PSO2

I can imagine that PSO2 Meseta likely out there we will still see someone wearing those old collaboration things even if they are not rigged up to the same criteria as fresh cosmetics in a similar manner and that there would have been outrage when it had been made obsolete or unusable. Collabs that have had their makeup removed still have their resources exist on the sport so those will probably still be available for jp players.

Only improvements we'll likely see is the new engine enhancing shadows...