Or they could just be wrong. They equate "no cell wall" with "primitive", when in fact the opposite is true. All cells have cell membranes, but cell walls are present in bacteria (prokaryotes), fungi, and plants, and not in animals.
That is what I recall from Bio 101 many years ago. Much has changed in biology since then, such as the kingdoms, so I thought they might be using the terms in a different way.