If he had HACE (or mixed HAPE/HACE which is common) it was clearly mild, and so recovery could be prompt. Not so with severe cases that are often irreversible.
The fact that the rangers put him on O2 and he got heloed out says he was indeed ill. Yet he was able to still do photos and videos? That is part of the problem with early HACE where the patient is only partly affected and might not recognize the issue.
See historical high altitude quote below
it is difficult for the stupid mind to observe how stupid it is.
George Mallory, Chapters IV-VI, X-XI in
Bruce, CG, The Assault on Mount Everest 1922,
page 129
