But it's strange that the page says that PostgreSQL includes support for ‘JSON’ data type and two JSON functions

In PG 9.2 there were only two json functions[1], but 9.3 introduced more[2]

[1]http://www.postgresql.org/docs/9.2/static/functions-json.htm... [2]http://www.postgresql.org/docs/9.3/static/functions-json.htm...