Yes, I know, you guys are going to hate me for the bump, but I didn't want to create a new thread, as this isn't really new news, just an update.
If your GCU is expiring soon, you won't receive this coupon until 5 days before it expires. My GCU runs out on Feb 13th and after contacting one of the social experts on the forum, this was the time frame that was given to me. (I used my last GCU discount + the coupon on MK11 Premium Edition.)
It does stack with the GCU discount, so plan ahead and accordingly. If you are using a debit or credit card, they will do a pre-authorization on your account, but it will roll off in 1-2 days.
Goodbye, GCU. (and Elite Plus membership; I can't see myself shopping at Best Buy that much anymore.) It was the best of times.