I'm sure he knows gaining muscle is possible, but I believe he was basing his answer more on being able to gain serious size and if he thinks it's optimal for growth. I personally don't know anyone who is truly BIG and ripped that regularly trains fasted or follows any type of fasting diet. Those who do carry a ton of muscle really can't afford to hold off on food if they want to hit their required calories for growth as well, which is also a big reason many bbers eat/recommend 5-10 meals per day...they aren't small portions either.