This is correct. fatness does not equal more high, increased length of the session equals more high.
so many people think that a really fat blunt/ joint will get you more high, however, if you take all the weed that makes it fat, and us it to add length to a blunt/joint of uniform thickness (around the thickness of a cigarette) it conserves the weed much better. i have absolutely no facts to back this up, but my theory is that your lungs have a fixed capacity, and since your breathing virtually the same amount of smoke in whether its a fatty or not, it comes down to the number of tokes you take. thus something that burns slower (less burning surface area) will last longer and in turn get you higher. this also means that 2 normal joints, get you higher than 1 really fat one, assuming you use the same amount of weed for the 2, as you would for the fat one.