[consilient]

> For some reason, many MWI adherents want to claim that this is not an additional postulate, that MWI only needs the Shrodinger equation, but it clearly is a postulate in addition to that equation, just as much as the collapse idea in other interpretations.

I think you're misinterpreting them (us). The claim is that MWI requires one additional postulate, whereas collapse interpretations need at least two: they both need a way to make distributions into probability distributions over observations, but collapse additionally requires some way of dodging Wigner's Friend type scenarios: an objective classical transition, extra state beyond the wavefunction, outright antirealism, etc.