Proc. parameters in Material assignment after BOM Explosion

Hi experts ,

Will like to ask a query

So , I have created a project using assembly process ,the project is successfully created ,
after that I'm doing CN33 Automatic BOm transfer of material X ,Y with reference points maintained in the activities .
Its been executed neatly , but in project when I checked for the material X in its proc.parameters the WBS which it is picking up is Level 1 WBS , instead of the WBS which the Component been assigned to NWA .
Though it can be changed manually but its not ethical way to do so ..

So requesting you to please guide and suggest what could be done to get the required WBS in Proc .parameters .

thanks
PC