It does make different predictions though. WMI essentially says there is only unitary evolution and nothing like a physical collapse. That means everything unit

It does make different predictions though. WMI essentially says there is only unitary evolution and nothing like a physical collapse. That means everything unitary evolution predicts will happen, unlike other "interpretations". This matters in at least two cases: (1) In a finite system (perhaps our universe, but doubtful), those other worlds will eventually come back into contact. They never go away and with only a finite number of states available, the splitting of worlds can't continue forever. (2) From a subjective perspective, there is always a future version of yourself in some "branch". Since you will become all future versions, you are subjectively immortal.