Yeah I saw that, good shit man.
Pullups are more lat, chins more bicep but still back too.
I guess that makes sense about parallel grip. I like doing those more now, lol.
I found an article that is similar to the other one I read regarding pull up grips.
In the latter situation you can do pull-ups without pain, but you're just not very good at them the problem could be with your elbow flexors. Your biceps are strong, and give your back muscles a lot of help on chin-ups. But on pull-ups, your biceps are more or less neutralized, with the arm power coming from your brachialis (a thick, strong muscle that lies between your biceps and your humerus) and brachioradialis, the forearm muscle that crosses your elbow joint and assists the brachialis in elbow flexion.
The neutral grip splits the difference all three elbow flexors are engaged, giving your brachialis and brachioradialis a chance to catch up with your biceps.
http://www.t-nation.com/free_online_article/sports_body_training_performance/things_you_should_know_how_to_do_1_the_pullup
That is the article, I also read somewhere that there is very little difference as far as back recruitment goes between the different grips as long as you are doing them through a full range of motion (chest to bar not just chin over bar).