Are you on fucking crack?
You can see Luffy's body during their initial clash. His skin is totally normal as their bodies are too far apart for the flames to get over to Luffy's body.
Later when they got closer we literally have several shots that draw Luffy the same as Kaido because the flames managed to break through and actually cover his body.
Do you actually read the same series? Lmao
How can one be so blatantly wrong and accuse the person that is right of reading two piece?