I would be seriously uncomfortable to discover myself making authoritative reference to anything out of a "pop neuroscience" book, unless I had myself validated the claim - at least as far as making sure there is a paper that says what is claimed of it, by whatever failed academic turned mountebank I am reading. (If those guys were comfortable being held to what they say, why did they stop writing for peer reviewers? I'm hardly an academic chauvinist, God knows, but if you want to be safe here in the 2030s, you really need to learn to spot a grifter...)

The tunnel vision you experience during hypovolemia is nothing like the "tunnel of light" reported in NDEs. It's just that you lose your visual field gradually, from periphery to fovea, as your visual cortex loses perfusion. In theory, a well-perfused brain dying for some other reason, such as a sudden complete loss of oxygen supply secondary to circulatory collapse secondary to fine VF or asystole, would retain the ability to "fill in" with something, the way our brains in normal operation cover the many gaps and lacks in our visual perception. (This is part of why I asked the other fellow not to bother me again about this at least until he knows what "ATP" means and why that is relevant here.)

It is strikingly absurd to imagine any of this does or can support a radically materialist conception of the universe. As I said before, materialism is exactly as religious as simulationism - exactly so, inasmuch as I expect to see a "solution" for the "mind-body problem" [1] around the same time as we solve the halting problem or constructively prove P=NP.

[1] https://plato.stanford.edu/entries/dualism/#DuaMinBodPro