PO: Default Promised date from Need bydate

Hi 

Planned orders released from workbench creates requistion and then autocreates to Purchase order. In this scenerio the promised date is blank in the PO where as Need by date is defaulted from Req.

There is a Profile option : PO: Default Promised date from Need bydate, When I set this at responsibility level it is not working as desired but if I set this at user level is perfectly defaulting PD from ND.  But this option with be not a right solution as buyers always gets changed now and then we have do this setup.

Purchasing guide say that this profile will also work for responsibility level setting also. But it is not working for us.