The more I think of it Law's R-Room same way how it prevented BM's power to reach to other stealing their souls it prevents her to give life also (like let's say prevent hee from making a rock homie when she fell doen or lava homie, or even homie based of the bombs she was touching)
While Law's df allows him to amputate things like elements too so he did that to Misery when he cut it down, when she is an actual element come to life