1. 4000+ calories isn't uncommon, it's not just in the book. The high intake is necessary for high activity and to sustain energy during high intensity training. The calorie intake itself isn't for mass, it's for energy. Think about Michael Phelps who takes in 12,000 a day while training. Also, people like me tend to not eat enough, and a 2,000 calorie diet really only supports moderate exercise for a so called "average" person.
2. HIIT, if done with running, helps with sprints and endurance for races like the 400m. Actually, during track a lot of the 400m workouts are very similar to HIIT, the only difference is HIIT normally only goes to around 30 seconds of high intensity to 90 seconds of rest, whereas my times will vary up to about 1 minute for intensity and 3 minutes for rest because I increase distance in a pyramid up to 400m.
HIIT is not beneficial to gaining mass, though it is to cardio which is very important to me as a 300m hurdler and 400m runner. I have the kcal intake to support the energy and I'm not doing it for an extended period of time so it doesn't really impact my recovery very much.
4. They did, but don't worry about it, I'm not offended easily at all.