Gaming

Don't want to sound arrogant, but most people here (including OP and the writers of the article) don't seam to know much about video game development.

Because statements like "... Isn't about graphics or frame rate; it's memory" don't make sense at all.

Because if you fast memory is to small you would either more often read from a slower memory which results in less frame rate or you would need to make the stuff that fill up your memory (most often textures) smaller (lower resolution) which "reduces graphics"

The article says something more business politics related: "Microsoft requires all games to run, feature-complete and without changes in quality or mechanics" on both Versions S and X. I'm not really believe this to be true because this would make the existence of more powerful X version completely pointless. However what I think can be the case is that Microsoft QA is forcing the studio to adapt the game for the series S before it could be published. This needs time. Since there is no low spec version for the PS5 there is no need for additional adaptations.