They are not equal and opposite propositions. One is deductive and accountable in its inference and the other is only mildly inductive and unaccountable in its inference.
We have to be careful of Pseudo-Theory here. And as well, understand the difference between hypothesis which propositions a
modus absens (something is non-extant), versus one which propositions a
modus praesens (something is). Just expressing a
modus absens denial in the form of a congruent counter-positive to a proposition is not automatically a correct framing. Such may not even constitute a hypothesis at all.
If the counter-positive bears no real structure of
hypothesis and accountability - then it is actually a
denial, simply posed in the form of a counter-positive. Such is the nature of pseudo-theory. The proposition that the mind is only the sum of its neural capacity and feedback dynamics, is pseudo-theory. It wallows in the luxury of unaccountability. It is the Kim Jong Un of mind theory. A tyrant, never having to produce anything nor be held to real scientific account. It can answer all four questions you posed, effortlessly so - and right now. It was able to answer these (and all) questions from the very first day the idea was proposed - but only from an
ad hoc fallacious standpoint. This is not the same notion as an idea's possessing explanatory power.
The contention that NDE's are extra-physical is a testable, incremental, hypothesis =
modus praesens. It places its set of incremental contentions at risk. By prosecuting that theory, we become more informed, deductively. By insisting on a non-testable
modus absens pseudo-theory which does not bear any incremental accountability, we do not get any smarter - only inductively confirm what we already 'knew'. The idea that NDE's are 'not extra-physical' - given what little we know of the domain, is NOT a hypothesis - rather the null - and if 'believed' is only an opinion.
In other words, the less we know, the stronger its gets as an idea. That is why you do not find its proponents too eager to test anything.
This does not mean that it is wrong, just that it is not really a hypothesis; and as an idea, is less scientific than we spin it to be. We can dress it up in fMRI color scans and neuro-speak, but it still remains only shallow inductive posturing with sciencey accoutrements.
Pseudo-Theory
1. Can be developed in full essence before any investigation even begins.
2. Never improves in its depth, description nor falsifiable or inductive strength despite ongoing research and increases in observational data.
3. Possesses no real method of falsification nor distinguishing predictive measure which is placed at risk, nor does it offer any other means of being held to account or measure..
4. Employs non-Wittgenstein equivocal/colloquial terminology or underlying premises (possibly pseudo-theory itself) where the risk of conjecture is not acknowledged.
5. Is employed primarily as a symbolic or fiat excuse to dismiss disliked or competing explanations. Is adorned with sciencey-like accoutrements.
6. Filters out by method during the hypothesis formulation stages, high probative value testing, in favor of perceived high reliability confirmation or authorized information only (
cherry sorting).
7. Can quickly (but not elegantly) explain a multiplicity of observations or even every non-resolved question (
Explanitude).
8. Is artificially installed as the null hypothesis from the very start. Falsification is completed and then forgotten, and the theory self-revives - the Theory from the Black Lagoon. It never goes away, even after being falsified, just crawls back out of the mud and is suddenly back in the discussion forefront.
9. Attains its strength through becoming a Verdrängung Mechanism. Is promoted through pluralistic ignorance and Lindy Effect or social intimidation.
10. Considers the absence of observation or a data collection/detection failure as suitable to stand in as ‘evidence’ (argument from ignorance).
11. Pseudo-theory can be identified in that, as less information is held or information is screened out (cherry sorted), pseudo-theory tends to appear to grow more plausible and more pervasively explanatory, and is able to be produced with less effort (armchair debunking for instance). Whereas valid theory and hypothesis tend to strengthen with research effort and an increase in information.
12. Is panductive – an invalid form of inference which is spun in the form of pseudo-deductive study. Inference which seeks to falsify in one felled swoop ‘everything but what my club believes’ as constituting one group of bad people, who all believe the same wrong and correlated things – this is the warning flag of panductive pseudo-theory. No follow up series studies nor replication methodology can be derived from this type of ‘study’, which in essence serves to make it pseudo-science. This is a common ‘study’ format which is conducted by social skeptics masquerading as scientists, to pan people and subjects they dislike.