@Kunal Gaurav​ yes, it is treated as a synthetic catalog. You can query it by using the convention "hive_metastore" as the catalog name. i.e. SELECT * FROM hive_metastore.schema_name.table_name

This will work for internal HMS, external HMS and Glue.

You cannot set any Unity ACLs on these HMS/Glue objects currently.

You can use the Upgrade Wizard in the DBSQL Explorer to upgrade HMS/Glue schemas and tables to Unity Catalog.