Aside for the mentioned reasons, there's a plethora of other reasons that orders could be getting shipped in a different order to what they came in. They could be printed off and the first for the day becomes the last in the stack, or they could have been sorted via location for shipping fees, or even slipped on the floor and been re-stacked.
Do you want them to waste hours trying to ensure that orders are in the order of availability, then time ordered? or have them use those hours getting everything out as quick as they can?
If you're impatient, remember, there was no promise to get them out this early, most were originally expecting late this week or even next week for shipping, so don't get impatient, it just makes everyone feel bad, including the guys at PS, and we want them in a good mood
