This panel is even better for the perspective:
In this panel, you can clearly see Luffy's compressed fist which makes up of Bound Man's entire body in width. It's also very similar to the panel above in terms of size. Or in other words, it's pratically the same stance. Compare both fists and it's clear both are the same size.
It's no doubt a CoC infused KKG, no matter what kind of nonsense sanjikun is on about.