I think within a few hours or days you'll get answers from some knowledgable posters on here. The only thing I can add is that they turned pro very young (MAB 16 I thought) so I guess they had little to none amateur competition experience.
These are inaccurate facts but close to actual numbers: EM had reportedly 114 amateur fights, won 108, lost 6. Had won 11 amateur titles in Mexico MAB had 60 amateur fights, won 56, lost 4 (he turned pro at 15). 5 time Mexican national amateur champion. JMM had 35-1 amateur career. Though he has the fewest fights, he was a two-time golden glove winner. Hope that helps.
damn..i didnt expect that many bouts. Usually mexican fighters just to the pros with hardly any amateur bouts.