Talk to me about Clone Vats

[Dustman]

Once you have all city districts build, start with the astrology project

...and so alchemy, and necromancy and spirit calling... wait, there are spirits out there

 

[alexti]

That neglects how many social special projects (especially those investigate aliens) there exist in game. Generally social teir 3 comes way later than engineering tier 3.

There aren't many of those projects that are worth doing early. In the strategies that aim for Engineered Evolution one would aim for this specific tier 3 tech, while in the engineering a lot of lower tier techs are rather important. Then just completing tier 2 in Engineering doesn't solve slot problem yet - you need strategic resources, so you need 3 slots (for 2 tier 2 buildings plus 1 strategic resource producer), so you employ 11 people in 3 slots while you need 15 pop to unlock them. The slot shortage only goes away when one or two tier3 buildings are unlocked.