Apple's Reminders app is so glitchy that your interview task probably would've been vastly superior to the actual consumer product.
For a long time I thought it was perhaps due to poor sync with the Mac, since sometimes I manage reminders from there, but the same thing happens with the wife's phone and she doesn't sync Reminders. She has a single daily reminder at 10pm. Sometimes it shows up 4 times. Sometimes 4 times and 1 disappears for a net of 3 reminders. Sometimes just 1 shows up. Sometimes none of them show up. It's bizarre.
I've stopped thinking about it as "glitchy" and more "the new Apple way".
Perhaps you should try logging off and logging in again.
I totally agree.
He let me reschedule for later that day but seemed hostile and grumpy throughout the whole thing. Didn't get the next round.