Portlets have the capability to create custom tables in the database. This is performed through <portlet>/WEB-INF/sql/tables.sql.
(Note that column descriptions have been added)
When migrating data from one database to another, tables.sql is not used. Instead, <portlet>/WEB-INF/classes/META-INF/portlet-model-hints.xml model definition is used to generate the SQL to create the table in the destination database.
Probably, this is done to support migrating to a different database (ie: from SQL Server to Oracle).
Extended info like column description is lost in the migration.
Allow to use tables.sql in Data Migration as well.
If destination database is the same as origin database, using the original tables.sql would allow these extended information to be migrated as well.