So I've looked into this and, if you've implemented an unmanaged BO (this is NOT QUERY), the "READ" method will only be triggered after Create / Update / Delete operation is executed, as the "Read modified entities" phase. A query scenario would trigger a "Select" method of our API if_rap_query_provider. The READ method of the BDef implementation, however, belongs to the transactional scenarios, not to the query case.

Basically, despite its name suggesting general read functionality, it does not handle initial data retrieval or general query operations.

Best regards, Rafael