I think he may have confused it with the Tau's alleged "father" species, those weird bees from which the eldar "made" the ethereals, and how theyve been kept purposefully separate from the Tau to avoid them finding out about their origins. It does beg the question of what purpose could the Tau serve for the Eldar :S
Isnt this moving into the territory of epilectic tree's now?
Are there even any actualy evidence on the tau being made by anybody?