The first list, Top Ten Western Native Perennials, represents native species that are found in the wild. The species with cultivar names (such as 'Blonde Ambition' or 'Perfect Pink') are selections that myself or others have made, by choosing the best plant(s) in a native population or group of garden-grown seedlings and reproducing it through selective propagation techniques such as division, cuttings or tissue culture.
The second list, Top Ten Native Perennial Hybrids, are plants that myself or others have discovered as garden-created hybrids. These occur when different native species are grown in proximity to each other and the pollinators (such as bees and hummingbirds) move pollen between the species to create a natural hybrid.
I have heard from some misinformed native plant enthusiasts that hybrids aren't "native" plants. I counter that they have clearly not spent any time studying native perennials in their habitats. If they had, they would have observed that hybrids are a common occurrence in nature, and in fact, this is how new species often evolve. Hybrids most often occur as climatic conditions change over time (such as rainfall amounts) and native plant populations expand and contract. When they expand and different species overlap, hybridization is often the result. Oaks, Yucca, and Opuntia (pad cacti) are three large native genera where natural hybrids are common.