So it's bad to stay in a weight division wherein you can't really make weight, another example is Casimero. he wanted to fight Inoue so he stayed in that division and in the first scheduled fight against Butler, he fell ill. And in the second one, he was caught with the Sauna thingy.
He was already struggling to keep the required weight, it's just too bad for Casimero as he was caught cheating, he could have just move up and be the number 1 contender to fight the champion. For Ancajas here, there's still one more chance for him to avenge his loss, if he wins here, people will stop doubting him, if he losses, then no choice for him but to move up.