He might be able to. Think of brick wall building:
Some people can understand the theory of building brick walls and have the practical skills, so they can build any brick wall.
Some people can understand how to build a brick wall but might not be able to understand all of the theory of planning what brick wall to build. So they would need someone to tell them what to build, then they could build it.
Some people can build only the exact brick wall they've been taught to build. So if it's exactly the same as the last one they built, they can do it, but if it's different, they can't.
Some people can understand how to put the parts together if it's made for them, but can't understand how to make the mortar.
Some people don't understand how building a brick wall works at all.
So you need to know what parts they can do and why they can't do the parts they can't do to know how much or what sort of difficulty they have.