How is it possible to win a 147 title belt below the welterweight limit?

[JonesJrMayweather]

Wow the fight was 3 weeks ago, time to get the fuck over it.. 2 lbs wouldnt have mattered, anyone with any intelligence knows that Cotto would have gotten steamrolled either way. So the only thing that really "irks" you is that his belt was on the line? So then in your eyes it would have made Cotto look better to have his ass kicked and still be the WBO champ after getting his face smashed up huh? Cotto agreed to take the fight and all its terms, put up a valiant effort and then collected the biggest payday of his career, thats the bottom line, move on.

cotto was a paper champ anyway, picked that dumped belt out of trash after Paul Williams threw it away.... Mosley is the real WW champ.

[Pavlik]

How did ODLH and Sugar Ray Leonard win title belts via catchweights?
How come they're not being scrutinized for that achievement?