Kuma did that once, it doesn't mean he can do it again.
Meanwhile Sanji has complete control over himself, Kuma several traits of who he used to be, Sanji didn't
And the implications of Judge's creations are more severe, since they are born in a way that they have no real feelings (Reiju learned through Sora but she said she doesn't feel shit, not even afraid to die) and they can't let them go from Judge's orders