B.S.
I had the same problem with one of my boys. Then I realized that he would always squat down to poop in his diapers or pants. He couldn't get comfortable at first going poop sitting up. So I got him a different type of potty, he was able to squat on it instead of having to sit, and that was that! After about a month or two I started holding him on the toilet without an adapter seat, so that he was able to to adjust a little, then we moved onto him sitting on the adapter seat. He just needed a transition. I should also tell you that it isn't working with my younger boy, who poops in his diaper standing up. But I have some time to figure that one out, he's just now turning two. The address below is to the type of potty that I used (not necessarily the brand).
Good luck!
http://www.babybjorn.com/American/products/Bathroom/BABYB...