What you are saying makes total sense. Just because you say you got in at 12:03 there could possibly 5,000 other people who got in between 12:01 and 12:03. So that means you could be say number 3,671 of 5,000 and that is just for that model. At the same times someone who ordered a less popular model could have gotten in at 12:15 and only had 1,000 in line by that point so they are being processed quicker even though they ordered theirs later.
It makes sense even if you were to go to a brick and mortar store. You could show up at opening and get right in line but say you end up being number 20 in line (so your processing time is the same but your queue time is different) but you want the model they only have 5 of and 10 other people in front of you also want that model then people behind you may walk away with their order first before you while you have to wait for what you want.