I too thought that because you just copied the "Specifically, why " have been ..................... how is this usage right ?" para from there, but what ron said is it is a idiom, and we cant have explanations for idioms, it is just the way they are. And we can always rely on Ron's post.
my approach was (may be wrong), i thought "appear to" is preferred to "appear as", and "equipped to" is better than "equipped for". I may be wrong, i think it is a problem from OG 12 ,if anybody has the official explanation please post here, that would be more helpful for the discussion.

check this post by ron of beatthegmat,
http://www.beatthegmat.com/post176512.html#176512

Here's the OE..does'nt make any sense to me 'cos for SC i rely on Verbal gurus like you..Its too much verbal-technical if you know what i mean!I prefer explanation in simpler terms..tell you what..you understand from this and then make ME understand:)Kudos for the trouble!!

Verb form; Diction
Because Neanderthals “disappeared,” the verb
describing their apparent abilities cannot be
present tense, so as equipped must be changed to to
have been equipped. Th e expression equipped to face
is clearer and more direct than equipped for facing.
A As equipped indicates that Neanderthals still
appear this way; equipped should be followed
by an infi nitive form instead of a
prepositional phrase.
B Correct. Th e verb tense clearly indicates
that the current evidence is about
Neanderthals in the past.
C As equipped does not indicate that
Neanderthals appeared this way in the past;
while individual Neanderthals may well
have followed diff erent paths, this sentence
is about the single evolutionary path taken
by Neanderthals as a species.
D Present-tense appear is needed to parallel
present-tense indicates and to reinforce that
this is current evidence about Neanderthals
in the past; as in C, paths should be singular.
E For facing is an incorrect substitution of a
prepositional phrase for an infi nitive.
Th e correct answer is B.
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