That is exactly what Zoro fans say. i'm using their logic. Even Nik87 said Luffy never trained his physical strenght during the 2 year timeskip.
Not only that but I can prove my point.
For Example, Take child Zoro at age 4, give him swords, throw him in the jungle and tell him to survive. This Zoro would never be as strong as he was pre time skip Zoro that he trained at the dojo.
The during the timeskip, have Garp teach Zoro haki, and then leave him to fight the Rusoskaina Animals, and figure it out on his own.
During those times above, have Zoro never lift wieghts, only survival and haki training.
The Zoro above would never be as strong as the Zoro we have now in the story.
That is exactly what Luffy is. Luffy never had any proffesional training.