I bet that it all stems from their decision to not only not develop it into a full game, but also to remove the playable teaser from the store; this active censorship, combined with the aura the teaser got, led scalpers asking stupid prices for PS4s with P.T. installed on different marketplaces. Providing it back on hacked PS4s & PS5s is a way to fight this obviously, but perhaps also some sort of a protest against Konami stand on P.T. availability in the first place.