JSON is not a textual format. What it is, is right there in the name: It's an Object Notation. Now, JSON objects are most frequently serialized to text, but they are still objects. The format is an orthogonal matter.
Why does it matter whether the exchange format is a regular or a context-free language? It is a textual representation of binary data either way.
Sure, it is harder to pattern-match context-free, and we have a convenient syntax for textual regular languages, but we create tools such as jq so that we can pipe JSON and extract data.
