My take is that they never managed to find a way to grow humans outside the 'ordinary' way. So they simply didn't have the technology to grow and sustain a working brains without also growing a whole human.
They can't just grow the human to adulthood, and then take the brain out and throw the body away? The point isn't to avoid growing a body; it's to avoid feeding a body that is laying there doing nothing, when the brain would have a much lower energy+nutrient cost.
I wonder if these imaginary super-AI couldn't come up with a solution, does that make this problem of growing just the brain a NP-HARD problem in this imaginary world?
