...serves as the one obvious distinction between the physical world and the perceiver within said physical world. And the perceiver has a sense that they are not abstract and are different from all other things within the 3D space.

The perceiver comes with inner thought. This is the internal voice of the perceiver, which they consider to be an extension of themselves, and the inner environment in which the voice is placed which feels as though it is not an extension of the perceiver.

The distinction between the perceiver of universe A and their inner thoughts can be made by comparing inner experience to outer experience.

Example:

Let’s say the outer perceiver decides they fear rollercoasters and refuse to get onboard. Upon remembering why they fear the rollercoaster they...