I don't know about this, it may be a defect, or, it may be the way DP 8 backup works. The iDB backup used a "IDB Integration" component, and is a BAR-type backup. Integration backups have always needed an on-line extension license
On the other hand, I have review the documentation carefully, and can find nothing that indicates that you need a license to do a IDB backup
I agree with Daniel, open a case, and get the official word