Interesting. I was under the impression that all passes were available as they are "taken", whether thats online or at the airport.
I agree, you really need to be right at the 24 hour mark to get the A.
We were in MK when I needed them, and Guest Services actually printed them out for me (the AKL) said they couldn't without me leaving the park and returning to the resort, which honestly was a disappointment. (especially since a moderate has done it for us before without issue) so, who knows.