yup. and training is within the rules of the sport. putting plaster in your gloves isn't, and neither is injecting elephant growth hormone.
since the rules are pretty well defined, every athlete who agrees to a fight accepts the risk of being hit as hard as his opponent can manage. but they sign up to fight someone with human abilities, because the rules state that the gloves aren't to be fucked with, and the opponent can't have any performance enhancers in their system. when they fiddle with the gloves or use PEDs, they increase their abilities beyond the accepted threshold, and well into danger zone.
i know you're just provoking a debate here, but some people actually do believe that getting that extra push doesn't matter. it does. it makes a huge difference in what the outcome of the fight will be, and it can mean the difference between giving a man a concussion and killing him.