if he runs sub-17 for the 5k, over 45 minutes to run 5.25miles he'd have felt like he was walking.
Basically over the 5k he's averaging 11mph or so, and 5.25 in 45 is 7mph. That would feel like a complete crawl... get the distance measured as people say!!
That's a REALLY fast speed, 11mph, I'd wager the stock ped-setting assumes a MUCH shorter stride length than you are producing. Your stride length is probably around 2.1 to 2.3m and it's assuming 1.6 or so for the average starter runner which actually works, because 5.25 would translate to 8miles or so with the increased stride length.
Ho-hum, you're dead quick mate, don't worry!