Yeah, he is. Marciano is S L O W and clumsy - almost to the extreme. Roy would bounce punches off of his head as if it were a speed bag. Roy puts on a counter punching clinic on his way to stopping the S L O W, clumsy Marciano in the later rounds. Marciano tastes the canvas about 3-4 times before the ref mercifully stops the slaughter.
People make out that RJJ had no power. He could KO boxers with both hands. Marciano would get blitzed with so many punches that he wouldn't know if he was coming or going. At Light Heavy, RJJ was the boss and im sure he could add a few kgs to fight at Marciano's regular 83/84kg weight. RJJ was 79/80 on the scales, just imagine his fighting weight!
I think Rocky sparks him out clean. Jones is great but Marciano is even better overall and very underrated.
The opposite is true with Jones. If he retired before the Tarver fight, nobody could conceptualise him losing in any of these matchups. I think if Marciano would have stayed a bit longer in the sport he would have been beaten big time and people will see his supposedly "awkward" defense as really a "crappy" defense that wwould be exposed once he faced a fighter who is not a smallish former MW nor an old HW.
Marciano is all wrong for Jones. Marciano fought the best defensive fighters of his era and can obviously deal with that style. Jones wont stop him so he will have to survive for at least 12 rounds. That wont happen. Jones gets hurt and stopped, likely in brutal fashion.