My take is that he couldn't beat them when they fought despite:

1. Outweighing Mayweather by somewhere in the region of 15-20lbs.

2. Pacquiao having been a Super-Featherweight only 9 months prior

3. Being able to choose the ring size, gloves of his opponent (I know this was definitely true against PBF) as well as them coming to a new weightclass stipulated by him.

He in no way fought them 'at their best' as they both faced several disadvantages when fighting him. Not to mention that the best version of Oscar being mentioned was only 3/4 years younger than when they beat him & a proper LMW. Neither has the frame to be a LMW. Put the best WW versions of PBF & Pac against the one that fought Quartey/Whitaker/Mosley 1 & for me they beat him.

They were also both considerably better at the lower weights than Oscar who largely passed quickly through them because he struggled with the weight.

People can talk about prime, but this isn't like Mike Tyson getting beaten by Danny Williams & Kevin McBride, he was up against guys who might well have had his number whenever he fought them.