Exactly - EVERYONE cuts weight. Sorry, but singling out GSP for cutting weight and using that as a reason to not consider him one of the best pound for pound fighters is ridiculous. Everyone cuts weight, with the exception of heavyweights, because there is no upper limit. So of course, Fedor doesn't cut weight, he doesn't need to. But everyone else in the lower divisions do. I'm not sure how much time is usually given between weigh in and fight night, but if you can honestly drop 30lbs for a weigh in, and gain it back WITHOUT getting out of shape, well then all the power to you. That's a lot harder than you might think.
Look, I never competed in MMA, but I did wrestle all throughout highschool and University. And even in wrestling, the ONLY time you maintained your weight to within the actual weight class limits, was for tournaments where they had a 2nd weigh-in AFTER the tournament - and even then, you were usually given 1-3kg of allowance (now, wouldn't THAT be an interesting rule to institute in MMA?).