Honestly, if you ask me, it's a bit of a gray area.

Personally, I think that if you had a reservation that was made in the promotional period and you helped Delta with an oversale you should 100% be able to use a voucher towards a reservation that will give you the Triple MQM's.

With that said, I'm not sure that the system will see the new reservation made with the VDB voucher as a new transaction with the VDB voucher as FOP, or if it keeps the same ticket number/electronic ticket as the original reservation.