This has nothing to do with my post lol, I'm not calling Sanji's attack weak because it didn't significantly damage Luffy. G5 has high resistance to blunt attacks.
I'm saying it's 1) insane that Sanji's strongest attack was paralleled with a Strong Right from Franky in any context, and 2) since its reveal, we've been hearing nothing but how hot IJ is, how the flame is so potent, how it's blue so it's the strongest flame in the manga above even magma-like flames - and now it couldn't even inflict as much burn damage as Mars' Boro Breath equivalent lol.
G5 is not immune to burn damage - there was nothing stopping IJ HM from burning Luffy up, but it didn't, because it's simply not as hot as magma or magma-esque flames. Hell, even Mars' flame seemed hotter, and that's just regular fire with no hype behind it.