Yes, totally understood and agreed they can't sell more than what's available (i.e. chip shortage). That said having a God of War for holiday could keep some from buying into a competitor eco system if they feel it's better to try and hold out for a PS5.PlayStation could have had 50 AAA exclusives. They wouldn't have sold any more or fewer PS5s.
Now, if both consoles had unlimited supply, then we would know how Sony having several first-party exclusives in 2022 and Xbox having zero (at least so far this year or currently announced) would have effected console sales. Sadly, that's not the world we live in at the moment, with the chip shortages.