Why are spiritual or religious planes of existence difficult to describe as physical multiverses?

Spiritual or religious planes of existence are difficult to describe as physical multiverses because they lack a well-defined physical and mathematical framework that connects them to our observable universe.1

In scientific cosmology, a multiverse is typically classified by the degree to which its constituent universes are part of a single, unified system. Models such as inflationary multiverses or those derived from quantum mechanics rely on established physical laws, such as general relativity or the evolution of state vectors, to explain how these regions exist or interact.1

Conversely, spiritual or religious planes are often considered "disconnected" because there is no consensus on how they might relate to or interact with the physical world. While some may believe these planes exist, the mechanisms for such interactions are not well defined by the physics and mathematics used to describe the observable universe. Consequently, they remain outside the scope of scientific inquiry, which requires empirical accessibility or a testable theoretical basis.1