I believe the authors have mainly succeeded in pointing out that such criticism is easily refuted under a multiverse scenario. Anything that can happen, must happen, therefore probabilistic sifting [which I view as what ISL was attempting] is an exercise in futility. The fallacy of such thinking is evident in this quote:
"For a start, how is the existence of the other universes to be tested? To be sure, all cosmologists accept that there are some regions of the universe that lie beyond the reach of our telescopes, but somewhere on the slippery slope between that and the idea that there are an infinite number of universes, credibility reaches a limit. As one slips down that slope, more and more must be accepted on faith, and less and less is open to scientific verification. Extreme multiverse explanations are therefore reminiscent of theological discussions. Indeed, invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator. The multiverse theory may be dressed up in scientific language, but in essence it requires the same leap of faith."
— Paul Davies, A Brief History of the Multiverse