"I'm not sure they are.
But if they are, it's probably because so much dishonest purchasers remove the Ultra from the outer box and swap it with a Fram Extra Guard box and that means big $$$ savings
If that occurs enough times, the product gets discontinued."
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Is that an assumption or an actually stated policy? As has been noted at this thread, the Fram Ultra oil filters sold at Walmart have a tight tape on the box, which is probably done to discourage what you note. In order to break the tape, the box will have a noticeable rip in it.
At last notice, Fram air filters at Walmart don't have the tape. Hence, I've seen Fram non-Ultra air filters in the Ultra air filter box.