Ok. Thats a good theory but I was also thinking that it might be something like, over time, he'll feel guilty about lying to her and will basically be like, "Hey Ladybug, remember when Alex became akumatized into wishmaker, how I told you that I never found out your secret identity? Well, I lied. I'm sorry I lied to you but I lied to you because I didn't know how to handle it but now I feel guilty about lying to you and believe that you deserve to know the truth. I understand if your mad. You have every right to be."
Something like that.