Not true actually if we look at bellamy as comparison point and say that at bare minimum bellamy grew at the same pace as sanji which is under the bar because sanji probably grew faster. Bellamy was strong enough pre-skip to ambush luffy with no damage inflicted and sanji did the same but we can see that luffy is able to take all that with no problem but when sanji did it it caused physical difference.Yes but he's also the only person, or one of the only, to fight Luffy while he didn't defend at all. You realize what you're saying is basically Sanji>Luffy's previous opponents because he did more damage than they did in the amount of hits he was able to land. Also Sanji is the only person to have scarred Luffy's face, the scar under his eye was Luffy himself.
Its not as much a feat as I bring it up to say in pure attack power sanji should still be about the same as zoro and luffy SHOULD BE
Zoro's 1000s worlds is mathmatically about the strength of a nuke (There is math I can show you)
Luffy's king kong pistol is about the same
And doing the math behind Hells memories with the area of sanji's foot and the rate of heat transfrer of a fishes body with the area of Watasumi sanji's kick imparted the same ammount of energy.
Theoretically they shoulld be the same physically just as a math stand point and a reference point obviously there would be a gap but I bring it up to show that his strenght is still massive.