I almost checked another copy of
Unfinished Tales when I posted that Alcuin
Is it correct?
if so I assume the phrasing is a bit loose, and the intended meaning is maybe that the resistance of the Elves of the West is outnumbered by the 'forces' of the East and South -- which can be gleaned from my section of the post before the quote, but that's how I take the meaning.
That said, I agree it does seem to say other Elves (again, if I copied it correctly) but why draw that comparison?