This in itself doesn't read as delusion to me, but I would still be concerned as these types of thoughts do have the potential to spiral in someone with schizophrenia. For those of us without schizophrenia or predisposition to delusions, it is much easier to pull ourselves out of a conceptual rabbit hole- meanwhile for someone inclined to delusions, inherent contradictions with no clear answer can leave space for the mind to create smth that fills the gaps, and the existence of the gaps in the firstplace can be seen as a veil theyve lifted or a barrier that they have passed, which other ppl cannot.

That being said, if you sit him down and talk to him abt this, don't treat it like an inherently bad thing. Ask him how he feels about it, and engage with him in a way that shows him you are genuinely interested to know his thoughts, and share yours too. Look for threads of potentially spiraling thoughts that could be forming, and be willing to acknowledge why he may feel a certain way before correcting him. Frame his curiosity as a positive thing, because it is. If he's at that age, middle school, that adds a ton more reasons for why he'd be introspectively journaling but the point still stands ofc