You seem to be describing "technical skill", like "can he move his pencil in a straight line". Essentially, can he draw the things he intends to draw on the paper?

I'm talking about "artistic skill", which is the ability to effectively put ideas or emotions into a work of art.

An analogy which might explain my thinking: A software engineer who writes a 1,000 line program in a month is producing work beneath their "skill" because they could've written a 100,000 line program that does the same thing, in that same month. Typing is a technical skill for programmers, but I wouldn't say that typing skill makes you a better software engineer.