It doesn’t make sense to make battle droids hyper intelligent. They are supposed to be mass produced, why would you make them expensive?
We see that they can make hyper intelligent droids, TCW has assassin droids and commander droids.
They are clearly more expensive, since some are uniquely adorned with decorations.
Astromechs would have to be on the more intelligent side, since they handle flying, mechanic work, navigation, etc.
The average B1 droids doesn’t need much more than chatgpt.
The 3rd party investigation found no evidence.
That doesn’t mean it’s true or not true.
In these types of situations, especially years afterwards, there is a huge lack of evidence, people forget, systems change and data is lost, etc.
The 3rd party investigation is done to reduce liability, not determine the truth.