This would be true if we were talking about something like String Theory, or Loop Quantum Gravity.

But it is not true for MWI: MWI was designed from the ground up as an interpretation of the mathematics and experimental results of quantum mechanics. It is designed specifically to not match all of the predictions of quantum mechanics, and to not make any new predictions. Other interpretations are also designed in the same way.

So, if the people creating these interpretations succeeded in their goals when making them, then they will never be experimentally verifiable.