Scylla db json support for insert with DEFAULT UNSET directive not working

I am trying the following insert statement with DEFAULT UNSET directive, but I get syntax error in the statement. I am using scylla 2.3.1. I tried to the syntax in Apache Cassandra and DSE. It works there.

CREATE TABLE user (id int primary key, name text, email text)

INSERT INTO user JSON '{"id": 1, "name": "Sam"}' DEFAULT UNSET

Following statement works in scylla. INSERT INTO user JSON '{"id": 1, "name": "Sam"}';

I have turned on experimental flag in the scylla.yaml to activate json support.