Ok, I think I know why at 6AM, the availability tool goes screwy. 6AM(for example) is considered a new day(ex. Saturday 7/26) and the availability tool checks for the next day, so my guess is that the reason why the appears sold out hours after saying their available(and the store is closed) is because they expect to sell out or are unsure of their numbers for the next day.
I went to the apple store today (Sat 7/26) in CT. They were open at 8AM. I was the 20th in line. They handed us tickets that guaranteed us a phone if we came back before 6PM(if you didnt feel like waiting in line). Each ticket varied based on the type of phone u want. There was a good stack of tickets. (thicker stack I'm guessing was for 8 GB black, thinest stack 16 GB black). The manager said they had lots of phones, quote "we haven't as many phones since the launch" So I believe they have a lot for this weekend, but it also depends on the store/state.