This is my thought on this. Honestly, I don’t think Conan would offer Kaito to the police even if he did discover his actual identity. If the police caught Kaito then I’d imagine he’d let it be, but I have a hunch that Kaito’ll also aid in bringing down the B.O. as well. After all, he seems to already know Conan’s identity (from what I’ve gathered) and seems to be helpful when Conan actually needs it.