That's a pretty nonsensical argument. The reason Sony has been so successful in the last five generations is because they always manage to have killer exclusives AND get most multiplatform games, meaning gamers end up buying Sony's console so they can play the bulk of the "must play" games each generation. Microsoft has been struggling because they didn't have that many exclusives, and said exclusive weren't really exclusive since people can just get a good pc and play them anyway, so less people feel compelled to buy an Xbox console. I never bought an Xbox because, why should I ? The few games I care about that are MS first party are all on PC, and I need a good pc anyway for work, so I'm hitting two birds with one stone without the need to buy two consoles and all the peripherals each generation. Gaming is expensive, and buying multiple proprietary hardware each gen is too much for most customers after all.
If all PS exclusives were to be PC day one, there wouldn't be a need to own a Sony console and to stay in the Sony Ecosystem. Heck one can argue what they are currently doing releasing PS exclusive on pc after a couple of years is probably going to backfire on them in the long run , as when next gen comes, I might not pick up a PS6 because, well, I have a feeling all the must-own PS5 titles will end up on PC eventually anyway with Sony's new strategy. Before I had to get a PS5 to get my God of War / Death Stranding / Ghost of Tsuchima / Bloodborne / Returnal fix... Now I just gotta be patient and wait a couple of years for the improved director's cut edition on PC... Again not sure it'll help bolster sales.
Imho the only company that should really reconsider their stance on releasing on other platforms is Nintendo. They have very little third party support, and always release crappy, outdated hardware anyway, so they would simply sell way more copies of their first-party if they were to release on PC / Xbox / Sony imho... Since many people don't consider buying a Nintendo platform each gen just to play a couple zelda / metroid / mario games. Plus they could still release quirky, gimmicky controllers and stuff for other platforms. At the end of the day , they would sell way more games if they were multi-platform, that deprieving themselves of tons of customers because they want you to buy 600 bucks of hardware each gen to play that mario and zelda game.