Everything else they had that auto redeemed still had it's own key that was separate from the promotion one. So I don't think it's a 1:1 match.
Psuedo code if they wanted 1:1
redeem(id, nv_code)
{
string mscode = nv.codes.get(type.GearsOfWar4);
windows_store.redeem(id, mscode);
nv.database.save(id, nv_code, mscode);
nv.database.invalidate(nv_code);
}
Their database can easily save everything and have that 1:1 association. All they would need is a list from Amazon for the cancelled preorders. Search in their database for those keys and put them in a list. Send to Microsoft and MS can revoke keys from looking at ID and code associated with it. I could code up that work in less than a day. It's all the other things that one has to worry about when invalidating and that's knowing intent because all the people you are hurting are potential customers (that could still buy DLC) and all the "bad guys" get away only to wait for it to happen again. That's why in most cases the companies just stop what happens, let the other guys go, and go after the "bad guys"