The argument is they'll open Xbox up to everything as a sort of sacrificial lamb and then go to regulators and say everything should be this open on all platforms and let consumers choose their storefront on any given platform. That actually makes sense as to why they'd keep Xbox around even as it's sales crater. It gives a purpose to it's seeming downfall.
Interesting speculative theory but I question if regulators would go for it because it would be very damaging to the home console market if walled gardens were ended and platform holders were forced to let anybody set up a store on their platform and sell content directly to consumers cutting them as middlemen out . It would demolish the business model.
The Microsoft CEO I could totally see playing a long game like this as he's ruthless. A fake pro-consumer stance to ultimately damage everyone at Microsoft's benefit. Especially sinister as some of these platform holders are promoting Microsoft games.