If it was in muscle memory it would be repeatable feat, and it really isn't.
Some work is technically polished and you can see/hear the effort that went into it.
But there's a point where extra effort makes the work less good. Music starts to sound stale and overproduced, art loses some of its directness, writing feels self-conscious.
Whatever the correlation between perceived artistic merit and effort, it's a lot more complex than this article suggests.