Similar to accelerating a PC porting strategy of shorter windows for big marquee non-GaaS 1P AAA games, or doing them Day 1 (or potentially even sticking with the 2-year window several ports have established), timed exclusivity of same games to then get ported to Xbox would destroy a huge chunk of the appeal and value proposition of PlayStation consoles to a sizable chunk of hardcore and core enthusiasts customers.
It's an inherently bad idea that gains nothing for PlayStation and gains a lot for Xbox, and just actively damages what selling appeal PlayStation systems would have to a good portion of typically highest ARPU spenders in their own ecosystem. Costs for AAA game production can be resolved through other means, such as (sensible) use of AI technologies in various parts of the development process, avoiding expensive licenses, less use of Hollywood actors/actresses and writers, etc. Which are things all devs & pubs can take on at amounts that work best for their targets.
If any platform holder is in a position where they would seriously need to consider a strategy of timed exclusives for eventual ports of all games to other platforms both PC & console, or Day 1 even for most of their 1P across the same, it's Microsoft. Sony will still have the MLBs and one-off things like a Destiny or Marathon show up on Xbox hardware, but that's about it. And Nintendo? Well, don't expect anything. Those two have shown they can grow their console businesses while still centralizing as much control within a stack they have proprietary ownership over as possible; Microsoft have failed to demonstrate the same for Xbox.
I've seen a lot of Sonytoo rumblings with regards to this. It's weird how Sony gets dragged into every bit of MS' bad news. Agreed with all your points, as well. We already know Sony refused Game Pass, a multiplayer game(s?) which would have required a XBL sign-in, and there's probably still more we don't know about. The sense I get is Sony are cautiously testing branching out with their own IPs, but only where it would make financial sense (PC, service games) while minimizing or eliminating the impact on their own ecosystem. Porting games to a rival platform with a small base (which does not spend as much on software due to Game Pass) would not make financial sense.