[sho]

Actually, "man" in this sense ("all humans") is descended from mann, an old english word that didn't specifically indicate male. It evolved to refer to males specifically later, although retaining its old inclusive meaning.

Also interestingly, the "man" in human is not related etymologically to man by itself.

So the author is actually correct, although the usage is a little archaic.

[pavlov]

This usage persists in Swedish where “man” means both the human male and a generic subject for a passive tense, similar to how “one” or “you” works in English.

Man måste vara fri -> One must be free

[yzydserd]

Yes, “mann” was person. Not related to “human” which derived from Latin Hominem.

A wifmann was a “female person” and a “waeponmann” was a male person. Wifmann contracted to winmann to woman.