"Tetrachord" typically refers to a series of four notes separated by a perfect fourth, not simultaneous notes, coming out of the music theory of the ancient Greeks. Although that may not be the intended meaning here.
The quote is not calling a major chords a tetrachord; it's comparing major chords to the set of tetrachords (whatever the quoted person has in mind; the linked paper isn't immediately accessible to me), despite not being a member.
Well, that doesn't make any sense either, as major chords don't have any perfect fourths in them either, unless you count the interval between the fifth degree and the tonic in an inversion.
For the harmonic convention of chords based on stacked fourths, I've always heard it called "quartal" harmony, but my knowledge doesn't go very deep there.
In any case, wikipedia disagrees.
> In music theory, a tetrachord (Greek: τετράχορδoν; Latin: tetrachordum) is a series of four notes separated by three intervals
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