A) It is a 3,000 + calorie ride. It is difficult if you are riding hard to take in enough calories, so when you are done riding, there is a significant caloric deficit.
B) A cookie or a beer after a ride is not going to result in weight gain alone. But if you were to then eat at McDonald's that night, and then a bag of chips later that night and continue this diet day in and day out...you might actually gain weight, even if riding this hard.
C) Again - when you exercise as you do, your appetite and cravings change in general. But long-term, it results in a healthier diet, in part because unlike sitting in front of a television, someone who cycles regularly can feel the performance difference between eating well and eating poorly. Watching television and playing video games…errr not so much.