Just seems like a likely repeat of PS2 to Xbox in terms of multiformat development to me.
...are going to make multi-platform games "interesting" this generation, to the point we may actually see less of them and far more games coming to one platform or the other (plus PC)
Development costs alone make this a nonsense from a hardware perspective. He also seems to have completely forgotten the existence of the Xbox Series S, which will be the weakest of the 3 and will also have to run all of the same games as the X and, in turn, what will possibly be the midranged PS5. The only way his scenario occurs, which it will, is when Sony or Microsoft pay for exclusivity to mitigate the costs, and even then the costs are so astronomical (I mean you've effectively got to pay for the potential loss of millions of sales) that it's timed exclusivity. To add to the risk, that's then prone to backfiring (Rise of the Tomb Raider is a perfect example of something that should have been a major release being a big sales disappointment on PS4; we may see it repeated with all this "exclusive content" for Marvel's Avengers).
It's a self imposed stipulation, but if developers out of necessity can get the new Halo running on an OG Xbox One and a Series X, they're not going to encounter too many hurdles getting their games onto an Xbox Series S through PS5 and Series X because they're never going to design a game that can't run on a weaker machine to begin with. Irrespective of different architectural strengths and weaknesses, there's inevitably common ground between the 3 systems, 4 if you include PC. Not that I expect the level of half-arsery that occurred for many releases on Dreamcast, which half the time made the console appear as if it had more in common with the PS1 than a PS2.
Basically the cut-off point for a multiformat developer isn't the Series X, it's the PS5 or Series S. Or in the case of Microsoft's exclusives, the Xbox One, which will then shift to the S...if we're going with the belief that's still real.