Of course, if they can cut him, then they should be able to cut Kid even worse unless you wanna tell us Kid is more durable than Kaido. Killer's punishes were working fine on Kid via Hawkins irrc. If you think it's just damage transfer, Apoo cut him pretty badly too. It's not their fault Big Mom has 0 skill at cutting stuff. Don't really get the scrap metal analogy. All the slashes that cut through these metals are either dodged or never aimed at Kid's body, to begin with. The scrap metal literally can't even protect Kid from a low-tier slash from Zoro. His only option is dodging or he has to get cut.