> GraphQL does not require a specific serialization format. However, clients should use a serialization format that supports the major primitives in the GraphQL response.
The section of the document you refer to is regarding the response, not the query-language itself.
From the document: "A GraphQL document is defined as a syntactic grammar" -- therefore GraphGL has a (one) preferred syntactic embodiment. The document goes on (in A
BNF style) to define the syntax of the language.
The language defined here is very close, but not quite, JSON - if it were JSON, they could have defined the semantics of GraphQL based on its structure (which could be surfaced also in XML, etc.) rather than defining any surface/syntactic form at all.
If this domain specific language had a huge value-add over plain JSON, it would be another matter, but the notational convenience is small given the all the tooling that you lose by not having be in a standard format.
