I noticed that too! And the strange part is that they were there a week ago! I'm wondering if they just ran out?
Hope so, as we have a trip to DL at the end of this year, and I've been saving my airmiles for park tickets!!
Maybe they are only listing what they have available. If I try to get WDW tickets, they don't have any parkhoppers and they don't have any 5 day tickets for adults.
That happened to me last year with the Sea World tickets. As soon as I went to redeem for them they were gone, but about a week later they were back and I needed more Airmiles to get them. Maybe they are changing the value for them. You could always call and check.