It is sad to see a competent physicist and capable writer spouting meaningless nonsense in order to advance his position in a “public relations race” of his own invention.
There is no difference of opinion among physicists as to what quantum mechanics predicts, and although Sean Carroll has done, and is doing, good work on exploring ways in which a geometry of spacetime might arise as a mathematical consequence from a suitable kind of quantum theory, this does not give any reality to the notion of the universe actually “splitting”. No competent modern physicist considers “collapse of the wave packet” as anything more than a model for approximating what appears to us to be happening when an isolated experimental system starts to interact with the external universe which includes us as a part – and (so) about which we do not have enough information to identify a pure state.
Source: How the Many-Worlds theory of Hugh Everett split the Universe | Aeon Essays