This is narrative that's designed to establish the evolution premise that the Angiosperms are the most developmentally advanced kinds of plants, and so therefore have the most recent origin.
Angiosperms Rise to Dominance
The Origin of Abundant Diversification
"Origin of reptiles, diversification of amphibians. Insects abundant." Here we can see how doublespeak is used to establish the premise that the evolution narrative envisions the development from simple to complex.