insert into multiple common table expressions givens syntax error

Reported by customer. Not sure if this is a BUG or a query that is not supported.

Here is the error that get:

1064 - You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '),ms2 as ( select subcategory, count as num_records from ms1 group by 1 ),mul' at line 1

Posting query in next comment that is available only to development.