Before epilepsy was understood to be a neurological condition, people believed it was caused by the moon, or by phlegm in the brain. They condemned seizures as evidence of witchcraft or demonic possession, and killed or castrated sufferers to prevent them from passing tainted blood to a new generation.
Free Will was always copium.
At the end of the day, brains are just biological neural-networks, taking in data and throwing out a result based on pre-built instincts and previous data/experience.
If you cloned a neural-network and gave both the same stimuli, you’d get the same result out… why would you expect anything different for the biological version of the same thing?
The only reason you’d notice two human clones diverging quickly is because it’s difficult to control so many stimuli, so they’d be reacting to different stimuli from the moment they woke up, and so would be building up different experiences to react by.