I'm a little confused by that.  It's sound advise when you're paddling an unloaded canoe, as the bow seat is usually closer to the canoe's center of gravity than the stern seat.  The bow will tend to pop up if there's only someone in the stern, moreso than if someone is seated in the bow seat.  This makes the canoe harder to maneuver and more "tippy".

However, in canoe country, a lot depends on weight distribution, portage landings, waves, etc.  Also, whether you're wet footing or dry footing has a huge impact on how you proceed.

I once guided a crew and put a giant of a teenage nicknamed Bubba in my bow seat.  He was probably 6'6" and 15 years old, and his sense of balance really had some catching up to do.  He's the only person I've ever had flip me out of a canoe when loading.  From then on, I was last to enter, and first to exit.