There were some great comments about how paleo diets affect muscle gain. I am surprised that the higher volume leg workouts produced more muscle gain - I have been thinking it still ultimately ties to food intake.
I do believe the big question is how much overfeeding or higher-insulin eating is necessary for muscle gain. I wonder if you can go high-insulin in the post-workout period and then go back to low-insulin the other days, attempting to get the best of both worlds. Conversely, maybe a person needs to overfeed for a sustained period to convince the body to build muscle.
It may be that traditional bodybuilding with its continual high-insulin eating pattern is unhealthy in the long run (as J Bennett pointed out). You have some people who have gotten big through traditional bodybuilding methods, and then they use an evolutionary eating pattern to lean out and retain their muscle mass. But I have yet to find anyone who started with a Paleo diet and gained, say 20 pounds of muscle. So it may become a question of how to gain muscle with the least amount of negative side effects, and then switching to a Paleo diet to maintain the gains.