Just because they've already finished doesn't necessarily mean that they will produce band 6's. They could have just rushed through the course, and the students have only a shallow knowledge at best of the content. But since this is baulko we're talking about, I doubt this is the case (at least for most of the grade), but I don't see the advantage of finishing the course this early, unless you're just going to repeat the whole course again for revision.
But to answer your thoughts, we have mechanics (projectile motion, SHM etc.), probability, perms and combs, exponential growth and decay, binomial theorem and applications of calculus to the real world. Quite a lot...