I'd like to agree with you, but I've worked supply chains like this before, it's never in order, everything is sanctioned into chunks. not all orders go into one massive queue for fulfillment. orders are classified/categorized into priorities, then big decisions are made about what "chunks" get processed and in what order... The queue is by chunk, not individual. Literally someone is making decisions about this queue not at individual iPhone levels, but probably chunks of 50K phones of the same exact size/color... otherwise how do you think they were able to get stock into the stores? Some pre-orders were put on hold to complete in-store stock orders... and don't forget this time we're competing with order fulfillment across 100 carriers requests.
My order was classified as in-store | AT&T | 32GB | Black | Residential Ship | and probably 5 other tags... that determined my priority, not what time I ordered. all 50K orders that are part of my Chunk will all get processed at the same time so it doesn't matter what time of day or even what day you ordered unless you were the 50,001 order he got pushed to the next chunk.
that's why you see the randomness. it depends on which chunk your phone is in.