Aren't the Drath extinct now?
Their homeworld was destroyed, but to the best of my knowledge the GCII campaigns never explicitly completely wiped out the Drath, and all that the GCIII Databanks seems to have to say on the matter is that the Drath have disappeared. As such, while the Drath are no longer (or not currently) major players, they are not necessarily extinct.
It should also be remembered that even when the Databanks pages seem to use language more explicitly suggestive of the extinction of the species, as with the Korx, it does not necessarily mean that the species has been made extinct (the Korath are said to have exterminated the Korx, with no modifiers to the statement suggestion partial survival of the species, in several places, and yet we find on the Civilizations page that the surviving Korx have joined the Krynn; part of this is likely due to a conflation of empire and species).