Wrong, it is because of Luffy's rubber properties that Red Hawk possible. Stretching rubber generates heat as rubber is essentially just a long chain of molecules that are all jumbled up and disordered; stretching makes it ordered, ie crystallised, and that generates heat. He channels the heat to his fist (hence, firefist!) and he channels all the haki there to withstand the contracting force generated due to the fact that heat makes rubber contract; rubber doesn’t want to be ordered, it wants entropy.
Hence, Red Hawk is a haki based attack that both has haki, boosted ap (contraction force) and fire
Hence, Red Hawk is a haki based attack that both has haki, boosted ap (contraction force) and fire