Service PR in ECC can not be created as SRM Local PO

Hi, friends

    I set SRM as ECS (extended classic scenario),  I create a  PR with service line and transfer to SRM ,  in performing sourcing screen,  I create PO reference this service PR, but the system creates a Backend PO not local PO.   PO creation of  no service PR  is normal with SRM local PO.

   Please tell my why, I think that it must have a Note provided to correct, Am I right?

   ECC: SAPKH61711,   SRM: SAPK-71311

  Thanks !

  Jesse.