The surprise is about their behavior, not about items received. In the situation I described, the discrepancy between the two times caused me to investigate further. 12 hours later, the same delivery schedule was still available. In other words, they deliberately misstated cutoff times to create a sense of urgency and discourage shopping around or having second thoughts before hitting submit. WTF?

In another instance - they canceled one item from an order, sent no notification of such, and completely erased that item from the order history. I was left scratching my head, until I reviewed emails to see if I really had ordered that item. Again, WTF?

I'm sure they're alright if you're constantly ordering things from Prime or whatever because there are more good instances to outweigh the weirdness, combined with their policy of crediting people to keep them happy and avoid breaking the illusion.