If the mathematical multiverse hypothesis is true, then that is the underlying unique reality. The different physical worlds perceived by different minds are different parts of the mathematical multiverse. Minds perceive the physical world they are embedded in, and there is a fact of the matter as to which physical world a particular mind is embedded in, just as within our own physical world, our minds are embedded in particular locations and we perceive those locations rather than our entire physical world.
If the mathematical multiverse hypothesis is true, then that is the underlying unique reality. The different physical worlds perceived by different minds are different parts of the mathematical multiverse. Minds perceive the physical world they are embedded in, and there is a fact of the matter as to which physical world a particular mind is embedded in, just as within our own physical world, our minds are embedded in particular locations and we perceive those locations rather than our entire physical world.