In the summer there are a lot of people going through Orlando so the A Lister count on a flight can go up quite a bit with business travelers still coming and going and EB check in purchases go up from the extra vacationers especially on early flights from what I have seen because not a lot of people want to be up at 5-6am just to check in while on vacation if they don't have any other reason to be up early. Also families usually try to go to/from Disney for cheap so a lot of people end up on the early flights as the evening ones sell out or go higher in cost and the early ones are much cheaper from my experience so one or more people from a family will buy EB and they board after pre boarders, Business select, and A Lister's so a B is not uncommon for checking in right at the 24 hour mark during peak travel season
Hope this helps
Blake
