I don't think this game was ever intended for release on PS4.
It has been pushed back twice or three times already and I'd say they always intended to delay the game beyond its May 29th release anyway.
Sony want this as a PS5 launch title.
Launch games don't make a lot of money. In the first 6 months of a new console there are usually less than 10 million hardware owners, it limits your potential sales.
It's why we never really see any "killer" system-exclusive launch titles any more. It's mostly cross-gen stuff for the first year (or two!) of a console, or cheap-to-make titles. It's totally different from the old days when games were quick/cheap to make and killer launch titles were viable & common.