Wow i didn't even notice, but I did feel something off, it's like he can't even comprehend his own existence or most likely doesn't want to, which could be an extension of of being introverted, most things introverted people understand cannot be understood by other since it usually only makes sense to us and we become lost trying to explain it to other people, which I feel is what is happening here but there isn't enough dialogue to himself to really ascertain what he is thinking making the readers feel lost about him too. During this entire time no one is really asking the right questions making the frustration even worse
I'd say these things aren't on purpose, more like the author being unsure in the beginning of how they wanted to portray Jio, but knowing this has a novel, wouldn't the author talk with the web too artist so the adaptation doesn't have these holes? So what's the exact purpose of blatant contradictions? The longer he stays inside the mirror, the further he strays from himself, retaining only very caricature-like traits of his self? But like you said, we don't have enough information to create any solid suppositions. The lack of proper communication between them is driving me crazy, they keep making logical jumps, like, just ask him, bruv
Not mirror, painting* lol. But yeah, later they confirm that humans feel like they lose their sense of self when entering the painting (when Ms. Cha entered), and Jio recognizes he said things a bit abnormal, things that he wouldn't say normally, after staying there. So I guess the theory of straying from himself while inside ain't fully discreditable

I'm enjoying this a lot, but it's also frustrating how contradictory this is. Jio had said he started talking so to not let people view him as an evil portrait and destroy him, but then he tells white-hair he talked because he was lonely. He also said he TRIED to create humans and only got warm corpses, and now he's saying he never tried because he felt like that'd be too much. He also was worried about his students and went to his art classroom because it was his favorite place, now he's talking as if he strongly disliked his work. This is really annoying, as if paying attention doesn't pay out, on the opposite
And in ch. 18 guild leader proposes the hypothesis of jio being a god, a hypothesis he himself had properly discredited in the beginning of the story…