I disagree. I play as 100% Discoverer with Kaelesh on all planets, except one that has humans. Here is a SS of my expedition haul today.
You screenshot proves nothing. Kaelesh have useless buildings, and you can have the Kaelesh researches with any lifeform.
Rocktal are the best lifeform production-wise, Humans can be better for discoverer miners if they fly a lot of expeditions each day. Mechas are only really suited for full-fleeters.
But Kaelesh? They are pratically useless.