20 pounds can probably be managed. But dropping 51 pounds in that short of a time. You can't drop that much in water weight and you probably won't have time to lose the rest of the weight, especially if you're in shape at 236. 30 pounds in like 35 days, as far as I know that's pretty tough if you're trying to lose weight "normally" (dieting and such). Some people more experienced in weight cutting can provide a more authoritative opinion, but it definitely doesn't look like he's unjustified in saying it's hard to do, and he's justified in complaining given the original fight was at 205.