My understanding:
If you have the new GM Card (in which you earn 1%, not 5%), you can use that with GMS. If you still have the old GM Card (5% earnings), you cannot use that with GMS.
If you have the new GM Card (in which you earn 1%, not 5%), you can use that with GMS. If you still have the old GM Card (5% earnings), you cannot use that with GMS.