The Gamma Knife technique is not just a cutting technique, it burns the insides, it's not really different from Akainu's punch other than Law's technique somehow doesn't damage the exterior of the body. There was literally smoke coming out from Doflamingo's mouth from his insides burning.It's true that the battle against doflamingo was one of attrition but that doesn't really make a difference to what I said. And even law landing his gama blade on doflamingo required support iirc. Also, it's not even remotely the same type of damage as what ace took from akainu. The gama knife is a simple cut which slashes internal organs. And doflamingo stitched himself back together because he simply took a cut. Akainu punched through ace with a lava fist. Akainu basically got rid of ace insides, there was nothing left that could be healed. If doflamingo gets a lava fist through his stomach its game over unless the guy can weave entirely new organs and a spine from his strings.
Law tag teamed Doflamingo, true, but Luffy fought against a Doflamingo whose insides had just been burned up by Law's most powerful technique. Even if he stitched them up somehow and was still crazy strong, I would never think Doflamingo was at his best for the rest of the fight.
I don't still don't agree that Luffy was that "clearly" superior to Law back then for the reasons I stated and even then may still be around his level for the same arguments I provided. So I can't agree on the implications of that.But... what this assumes is not that law has grown as much as luffy, this would imply law has grown more than luffy. Because law was clearly not as strong as luffy back at dressrosa. So if the possibility is raised that law has managed to caught up with luffy then clearly the implication is that law's growth has to be greater than luffy's. But regardless, luffy's growth has been entirely extraordinary and there is zero evidence anywhere that law has kept up or caught up. same goes for the rest of luffy's peers.