I paid part of my college tuition acting as a handling coach, and I will be honest, if a kid of Jaylen's size had his handles, I would be drooling.
Calling it horrendous is an over statement. The kid has good handles for his size, and one day he will get to the rim at will because of it. Now, he makes the little mistakes, and it is a bit loose. It is almost as if his talent is ahead of what his brain can process in a short time right now. Seeing as he is so young, it will change.
And he needs to tighten it up a bit, and get in a lower stance. But at 6'7, he has all of the green light mechanics you want to see out of a handler.