I'm not sure what "process blindess" is nor have I read the book that is the subject of the interview but I'd venture a guess at what doubters might be getting at. They might ask how we could be sure that the blind person is "seeing" in an NDE or OBE in the sense that a sighted person understands seeing. After all, we can't see what they are seeing. So they might be arguing that the brain concocts some pseudo-visual imagery under these circumstances.
I don't want to be setting up a straw man to knock down so perhaps others can explain what is being claimed by the authors. However, if what I have speculated is what they mean then I would put the explanation alongside all the other "delusional" explanations that are put forward by the physicalists. In other words, if the experiencers can't be accused of lying then they must be delusional.
Something that lends weight to the blind-who-can-see claim is the reporting of 360 deg vision as a feature of some NDEs. Clearly this cannot be perceived by front-facing physical eyes so it will be dismissed as hallucination. But to someone not tied to the physicalist assumption that perception is limited to the physical body, the idea that the disembodied mind/soul/self can perceive as well, if not better, than the limited physical body, this is not surprising. That, of course, raises the debate to a whole new metaphysical level involving the nature of what is "out there" or what is created by the mind.
https://www.ted.com/talks/donald_hoffman_do_we_see_reality_as_it_is?language=en#t-826732