So here's the problem. Most yeast strains are alcohol intollerant. So as your beer attenuates, it inhibits the yeast from doing their job. Bumping the temperature a bit towards the end of attenuation will help the yeast finish the beer out. The 2 pounds of corn sugar in the recipe is going to attenuate pretty quickly. That kind of sugar will impart a hot-alcohol kind of flavor if you ferment it too warm. This is mainly why you want to start off at the lower end of the temp range. That said, the Belgian yeast strains, add some pretty interesting flavors at higher temperatures. Mainly spice and fruit-like flavors.
Personally, I would ferment this starting at 68F for a week and then bump the temp 1 degree per day for the following week. Leave it at 75F until fermentation completes and then rack to bottles or keg.
I'm a little interested in the fact that there are no dry hops for this IPA. In fact, the entire recipe seems a little hop-light to me. Plugging the recipe into beersmith, I get around 65 IBU which is on the low side for a double IPA. Perhaps the recipe intends to feature the yeast more than I considered?