Most trainers will tell you and I agree that a puncher is born with it. I think its the same for chin. People who are not heavy handed naturally can get the most of what they do have with proper technique. In the Bradley v Rios one has to take into account how serious Rios took the sport and how long he's most likely been doing diuretics. The guy announced his retirement right after the fight and has always seemed emotionally unstable. I think he kind of gave up in that fight to be honest.

Its possible however that Roach discovered something in delivery that somehow was missed over an entire career but I think it was more about Rios then he was about newly discovered Bradley power.
Hearns was brought up and in his case, he only had about 10 ko's in 165 fights as an amateur. Was the power not there? Sure it was but here is where "technique" would appear to change everything but the power had to be there for the technique to shed results. As an amateur Tommy was fighting a silly scoring system and had all the advantages to merely out score the opponent and never plant a shot. The system prevented Tommy's natural born power from shining through.