Kali was now faced with a difficult decision, and that was how to go about finding out if Arad is aware of himself as AO or not. If he is aware, then that's a huge problem for the gods. Soon, his growth would explode as more of his power returns, and it risks him losing himself in the process.
She can either press him to find out or leave him alone. If she made the wrong decision, then she would be dooming everyone. Neither of those two options was good enough, so she had to use her authority and wisdom as a goddess to force a third option, and it wasn't that difficult.
She would train Arad to endure the possibility of his knowing the truth. If he knew that he was AO, it would save his mind in the future, but if he didn't know, she would have just put him through useless and exhausting training for no reason.
