A variant unique to cited text

When a substantial chunk of the Bible is cited in some ancient work and within the manuscript tradition of this work new variants happen, do they count for anything? Well, at the very least they give us another fresh set of stuff to study.
Take this example from Kosmas Indikopleustes, citing Acts 17:26, εποιησεν τε εξ ενος παν εθνος ανθρωπων (He made out of one the whole human race):

The last word on line 2 is εποιησε, line 3 continues with τε εξ αιωνος παν εθνος αν̅ων (He made from eternity the whole human race). ενος (of one) and αιωνος (of eternity) differ phonetically only in the added syllable /o/ in the latter. Phonetics made the error easier, context did as well: the whole of the context is devoted to arguing that heaven is 'eternal'.

Image is from Plut. IX.28, but there is also another Kosmas manuscript with the identical error. Until we find a Greek biblical manuscript with this variant, most of us will never see this one again (except for the poor student who is going to study the text of Kosmas's bible - any takers?)