This is part of a plan to crack the market Nintendo dominate. The starter player. People tend to be loyal to a console/handheld even when another is doing better. How else could someone buy the Series X/S day 1 after the mismanagment of the XBone generation?
The majority of Sony IP is aimed at an older market than Nintendo's. Using a combination of small external studios using established IP like Lego combined with Sony IP, and Sony building its younger first party portfolio on its Astro IP will get younger children to consider the PS at an earlier stage. By leaving Nintendo to the younger market, you could end up with brand loyalty and not buying a Playstation as a complementary console.
You are doing it wrong if you release your games on the platform you DON'T want people get loyal to...
Or do we want to pretend Xbox might be doing the same with their PS releases?