You need to ask yourself why no one can take you seriously? The answer is quite simple, you never back up your pronouncements with primary sources and so they are just your opinions and,as such, carry no gravitas whatsoever.
At least I know what I’m writing about. My guess is you are European. Few from Europe have a good understanding of US boxing history. Typically a distorted view.
One of the greatest writers on boxing was Hugh McIllvanney ,a Scotsman. Reg Gutteridge was also very well thought of globally.
If they believed Frazier was not a slow starter they were too far removed from the US boxing scene to pick up details.
Toss up fight for me. The only thing I feel comfortable predicting is that it'd knock the prime out of both men
You have 2 sluggers who are there to be hit. One thing that would certainly be a factor is accuracy. Every fighter misses punches but the degree Marciano would often miss by can't be overlooked. He would miss by wide margins leaving himself wide open. Frazier was very precise with his hooks. Accurate and his punches were shorter. Marciano is gonna be more open to the clean punch. That is where Frazier gains separation.
It's a myth that gets parroted in my view. He generally gave up the first round or two tops (and thats against his best opposition) but by then he was in his rhythm and then look out! It's not like he was a moderate puncher who could only wear a guy out in the last rounds of a 15 round fight. He was a damn solid puncher who could stop lesser opponents early but who carried his power late as well which served him well against more durable guys.
I favour Frazier on points or late stoppage on cuts. Rocky has a puncher's chance, though. Remember Bonavena?