Even those who are definitely true naïves aren't always simple to talk about. One French painter in the book paints the Rouen Cathedral as this gloriously intricate pointilist thing dappled with bright candy colors. At the same time, all the cars he paints at the base are semicircles with two wheels each. The way I drew cars when I was five, basically.
Of course trained artitsts have imitated aspects of naïve ones since the nineteenth century and still do. That muddies the waters too, in an interesting way.