A coordinate system is an abstraction, whether anything has some large coordinate is irrelevant to the coordinate system itself. But my understanding of MWI is that there is discernible state being described by the Schrodinger that is taken as "real" or "concrete" by MWI. If we considered the non-actual branches as merely abstract coordinates, then there would be no problem with profligate state and its associated theory cost. But then it wouldn't be many worlds, but rather some kind of collapse theory.

Wavefunction state is just as “real” in the Copenhagen interpretation. There cannot be any hidden variables, it is not merely a mathematical abstraction. You then must posit this additional process of collapse

Where the MWI takes additional theory burden is where it explains how the born rule translates to our lived experience - ie. why do we only experience one path of the wavefunction