T&C now explicitly limit the denominations of GCs that are eligible for rewards -- up to $2000.
Purchase Conditions
Please note the stated reward is for gift card purchases made between $25 and $2000. No rewards are given on any Gift Card purchases over the value of $2000 denomination
It seems to me from the wording that you can purchase multiple $2000 cards in the same transaction and still get credit, but I haven't tried it (and won't unless they offer 2x points again).
Another note -- I did receive credit for the Business gift cards i purchased a while back. All told, netted 19911 points for a total cost of $90.