Good stuff here. I agree with the post about boxing cardio and mma cardio. Boxing is very aerobic and if you can stay relaxed and are in good shape, you'll be okay. But BJJ like wrestling, and unlike boxing invokes muscular fatigue. The lactic acid buildup in your forearms and shoulders combined with the aerobic nature of pushing and pulling a resistant 200 lbs can make even the best boxer gas out in a few minutes.
I understand your point but Boxing has more muscular endurance than most people realize; legs and especially shoulders.
If you notice when a boxer gets tired their first instinct is to lower their arms.
People have to remember its not just about stamina but also about taking a punch, taking a blow to the body or face not only hurts but zaps energy very very fast.
Exerting yourself by loading up on every punch will drain your energy quickly aswell.
Also you have to take into account other variables such as the tempo of the fight and the opponent, does he punch hard? Is he a runner thus making you chase him? etc etcc
There is actually alot of wrestling in boxing with all the holding, if you are a brawler then you will want the opponent on the back foot and against the ropes. So naturally there will be alot of holding once you get up close.