bug or intended behavior: customSQL=true doesn't exclude includeFrom fields

tested with SmartClient Version: v9.1p_2014-07-15/PowerEdition Deployment (built 2014-07-15)

I'm starting a dedicated thread for this question:
http://forums.smartclient.com/showpost.php?p=121296&postcount=2

A field includedFrom a related dataSource will be included even if marked as customSQL=true, and also will be included the tables in the generated $defaultTableClause.

It restricts the usefulness of the includeFrom. Is it a bug or intended behavior?