Well, I have to agree with them - SWIM's general tendency is to overshoot the mark, I don't know why. So if one says OK, 60mg of this X, Y, Z stuff is a good dose, SWIM's gonna think, yeah, lets double it and try!
But just for the history, SWIM's first try was with 100mg. Awesome! SWIM actually passed out before actually smoking all of it. He knows that because after coming down, his pipe had enough spice left to provide him for another decent journey (estimated nowadays as a ~30-40mg trip)
Maybe one reason for overloading is that amidst fears of incompetent smoking technique, one tries to load more than necessary to compensate for possible spice losses (burned spice, not full inhalations, etc. etc.)