It assumes a hard step between wildlife and sapient life, but it makes no assumptions about earlier hard steps.
I suppose it's not likely to be a hard enough step that creating enough life to massively outweigh it is all that hard. Wildlife will only live on the surface of one planet. Sapient life can live on many planets, and can mine them as so to use all the matter.
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.