You're just making 0 logic at this point.
Could law use shambles? No, ig not on him, for argumentative sake.
could law slice him in half like I originally thought? no, ig not, for argumentative sake.
However, your whole take on the gamma knife is bonkers, clearly it does not care about your haki (Like the one Jinbe has. Gonna clarify this before you point out Big mom again for having a way stronger offensive and just more resilient one and some-how compare it to Po: Fish Edition) or physical defense which is why he could get the upper-hand on Doffy. You can say whatever you want about "needing luffy" or "could only surprise with luffy", but from what Im aware of, luffy and law switched places, using shambles, and he used gamma knife. Thats it, thats all luffy included in. Made doffy confused that he was there and thats it, doffy's fault, has nothing to do with luffy even.
Also ignoring the fact law can use Color of Armaments "on a whim", which did help him bypass Vergo's defense, which should absolutely be included in the comparison of one "coat myself in metal for defense" person vs "coat my forearms in metal for defense" person.