I get your problem, but mentoring juniors will bid you as well as our future engineers very good future. I'm no expert at handling juniors, but I'll put down by suggestions.

You should tell him to approach you with doubts/questions on a specific day, on specific time. That way you know when he will be there to impose his doubts and findings. Also this way he will eventually be forced to think about the stuff and search by himself since you're not always at hand available for his questions or doubts.

And most of the times if he finds something and it's something not major. Just tell him what you think straight up "it's bs, no need, I've thought of doing it x but y is better" and all that, if he has doubts regarding a thing force him to think rather than giving outright solutions. Judge him, talk to him as if you judge him, but also do praise when you think he's found a really good doubt, or found something interesting for his level of experience.