I don't recall them actually showing the actual range the Olympic archers were shooting at. I have to agree that I thought competitive archers could do better than that at that range.
That said, it wouldn't surprise me if Brees was an above average passer in accuracy. Based on the passing competitions the NFL used to have around the Pro-Bowl, most of them are not pinpoint accurate. Hitting moving targets and knowing when and where to throw the ball are more important.