identity probably refers to the βISβ:
SELECT js, js IS JSON OBJECT "object?", js IS JSON ARRAY "array?", js IS JSON ARRAY WITH UNIQUE KEYS "array w. UK?", js IS JSON ARRAY WITHOUT UNIQUE KEYS "array w/o UK?" FROM (VALUES ('[{"a":"1"}, {"b":"2","b":"3"}]')) foo(js);
Like these?
> Adds SQL/JSON constructors, including JSON_ARRAY(), JSON_ARRAYAGG(), JSON_OBJECT(), and JSON_OBJECTAGG().
Not sure what SQL/JSON identity functions relate to