I kind of like the author’s approach to this not-so-plausible sort of scientific speculation. Carl Sagan famously drew a line between the scientifically plausible and implausible sorts of speculations. There is nothing wrong in theorizing about other universes, but it’s a little far-fetching to go beyond what can ever be empirically supported/disproven, in other words dogmatic. This brings us to the question could there ever be a theory of multiverse? To which I must answer, yes but it should have the same scientific standard as any other cosmological theory.
That is to say, we should still seek an empirical basis for whatever can be hypothesized about alternate universes. A cosmological theory may indeed posit portions of a multi-verse that may lie out of our means of direct observation, but we still need a rather extraordinarily convincing kind of justification for such an extraordinary hypothesis.