Because someone with a substantial amount of lean tissue has to diet in a way that sustains that lean tissue while burning fat. It doesn't facilitate the type of drastic losses of weight that you see elsewhere. You can consider it "douchey" or whatnot, but the fact of the matter is just that someone who is in training and sustaining performance faces a different situation than someone who is just in the "I am a fat guy who wants to lose weight" situation.
And I literally meant that I did not mean disrespect to Gorilla: he understands (and we all should per his training log) that his training parameters are (or at least were) entirely diet/weight loss focused, with his weight training ultimately facilitating a lean physique with some degree of muscle mass. He's squatting with a dumbbell standing on two chairs--not trying to improve in a lift that places substantial demands on his CNS or overall body musculature. He has limited equipment that facilitates only doing a lot of exercises that don't involve very heavy loads. It's just a different proposition than training for powerlifting, yet one that makes a dramatic weight loss much more feasible.
That is not to say that you can't lose a substantial amount of weight as a powerlifter; instead, it's just that you will not see the type of dramatic loss in a short timeframe OP asked about (or that Gorilla saw) within training parameters that aren't friendly to that type of goal. Gorilla's protocol was friendly to that type of goal. I can't imagine a reasonable powerlifting training program that would be: instead, weight loss with powerlifting, setting aside the immediately-pre-competition loss that Pwnisher references, is just a steadier, more responsible/reasonable type of weight loss.