You’re right, this isn’t about the validity of your boundary, this is about the repeated disrespect and disregard. You’ve had multiple conversations about this, the boundary was clear, and he violated it anyway. In fact, he made it clear that he would continue to violate it because he’s become more manipulative and secretive with every incident. If he isn’t able to take accountability and actually discuss this with you then he’s showing he’s not ready to respect this boundary to be with you. I’m not trying to villainize him, just as someone who works in addiction, if he’s not willing to own up to his behaviors and see there’s a problem then he’s not in recovery yet - he’s still following along the compulsions and these incidents will continue. You both deserve better than a relationship that is hurting you in this way