Downvoted for the personal attack on the author, but in a spirit of using this as a learning opportunity...
The writer obviously groks SQL. SQL as a language expressing relational algebra sucks. It was a way of trying to make relational algebra "grokable" by end users, in the same way that COBOL was a way to make "programming" grokable by end users.
The author's point is nothing to do with JSON, it's about having a column type that contains structured data.
In "pure" SQL you have to extract that structured data into another table or a hack like "subtables" or something.
The "natural" form of a lot of data these days is JSON. Having a JSON data type is only the start of being able to query it cleanly in SQL.
For SQL to cleanly support JSON, it needs the ability to handle the lack of data types in JSON, and the fact that each JSON element can be an untagged union of potential types.
