Re: Postgresql have json for years.
Oracle has had JSON support and JSON indexes for years too. Ever since Oracle 12.1. This is just a new data type that was included mainly for performance reasons. All the JSON functionality added over the previous 4 releases (12.1, 12.2, 18, 19) works just fine with the new data type.
If anything, Oracle are confusing people with this new data type, because uninformed people will think it's Oracle's first steps into JSON.