I’m gunna disagree with you XML comes with validators and versioning as part of the XML spec. You can validate XML files against XSD descriptors that can be published and even referenced by the XML file.
The only downside of XML over json is that XML is verbose AF.
Strict validators, versioning, checking, and definitions is EXACTLY what you want in a storage format.
ODF is also XML. It makes sense here.
More information for you: https://en.wikipedia.org/wiki/XML_Schema_(W3C)