Actually, there are a number of factors that affect the performance of cantilever brakes.

One that surprised me is how sensitive they are to the shape of the triangle formed by the straddle cable. If the base of the triangle is too narrow, they won't retract. If it's too wide, the "feel" at the lever sucks. In this case, if the cable hanger was placed on the unicrown, the triangle would likely be too wide.

Another issue that has come up in the past is what happens if the brake cable happens to snap. The earilest versions of cantilevers used a straddle cable that connected the two brake arms. If the main brake cable snapped, that straddle cable would snag one of the tire lugs, lock up the front tire, and cause the rider to perforn an unintended forward flip. The front reflector bracket on this bike was designed to catch the straddle cable in that event and keep the flip from happening.

These particular Shimano brakes have an additional design feature that addresses both of the issues that I mentioned above. These brakes have a link wire that replaces the straddle cable. The link wire both controls the shape of the triangle and allows the brake cable to pull through, rather than catch a lug, in the event it snaps. That's why I said that I thought they were one of the better designs.