I also had trouble understanding that sub-clause. Maybe we read it in our head with the wrong emphasis:
its behavior can only be intelligent when it is exercised on the training distribution
Meaning: The agent gets inputs that are within the training distribution. ↔ The agent behaves intelligently.
But I guess it’s supposed to be:
Meaning: A behaviour is intelligent. ↔ The behaviour was exercised during training on the training distribution.
I also had trouble understanding that sub-clause. Maybe we read it in our head with the wrong emphasis:
Meaning: The agent gets inputs that are within the training distribution. ↔ The agent behaves intelligently.
But I guess it’s supposed to be:
Meaning: A behaviour is intelligent. ↔ The behaviour was exercised during training on the training distribution.