I did read the original link but honestly don't really understand. Seemed to be some kind of argument there has to be a multiverse to account for the expansion

I did read the original link but honestly don't really understand. Seemed to be some kind of argument there has to be a multiverse to account for the expansion of the universe. That seems like a weak argument to me because in my understanding we're not that sure about what's happening to the universe and cosmologists keep changing their minds. Regardless, I didn't quite follow what sort of multiverse they said it implied and how it differs from MWI. Going by your comment, I'm not sure there's as much difference as you may be suggesting. Deutsch's MWI is full of what we might (or might not) call "pocket universes", it's not focussed on just big universe sized branches. I saw the article talking about the wave function spreading out which I think is the same concept Deutsch talks about in BoI with fungible instances of particles spreading out (a multiversal object is a collection of instances).