Or it is just corporate greed. Samsung would love to position something that is just okay into a premium price tier and not have to pay Intel. Sure they’re going to pay Qualcomm instead but you can bet that Qualcomm is giving some great introductory prices to their early partners.
The only things JSON has over xml is that it’s easier to write a parser for it and the format is less verbose and less complicated. There are extensions to JSON that can add features that xml has and the JSON spec doesn’t have. Overall the xml spec is bigger and has more features but that also makes it overkill for many of the cases that it would be used in.