Regarding the weight issues, yes it is difficult to maintain it, specially if your body is growing and can't adapt to your supposedly weight categories. That's why there are different type of weight classes, so that boxer can fit where they height and body will go. Then go up another notch like what Manny did during his prime and beating large fighters. So for Jerwn, and it the news is true that he can't make the weight properly then it will be a very dangerous fight for him and most likely he might lost again. But if his team are good at working with him round the clock to check how his body is losing that weight, and not body mass, and then still retain his power at absolute peak prior to the fight then they do a good job and most likely Ancajas will have his revenge.
We make it a big issue and yet Ancajas can still make it to the weight requirement. I think what Ancajas has to focus is to improve his stamina, it's not the weight that is the problem but his Ancajas because if he gets tired easily, he will lose his power in the later rounds, and that's what happened in their first meeting.
Weight cutting is a huge issue when a boxer is rushing to make his weight pass the weight limit. It is one of the major reasons why boxers lose. Pacquiao's early losses is due to him rushing to make his weight pass the weight limit but failed. And most of the catch-weight fight of Manny Pacquiao had him dominate the fight because his opponent is fighting at a weight limit they are not comfortable with. I honestly agree with this article[1] even though I am a Pacquiao fan.
So do not say that weight issue isn't that big.