The AI uses workers even when it doesn't have the minerals to do so.
As you can see on the Screenshot taken in observer mode, the Togra-University AI assigned a whoppin' 5 workers in their capital, when 1 would be enough to spend all minerals.
This means they are just wasting the potential of 4 population that could be doing science instead.
So the algortithm that assigns the workers is essentially broken!