Great article Jason, thank you for sharing the link here.
Either I am misunderstanding the responses or I'm afraid most of you are missing the point of the article. There was no assertion that Brahea edulis is literally native to the California/Baja California mainland. Guadalupe Island is just as 'native Californian' as are the Channel Islands north of the border. Together with the mainland these make up the California Floristic Province whose borders are what naturalists and scientists use to more accurately define uniquely Californian ecosystems and their flora. As I understand it, the article is hypothesizing about how appropriate B. edulis is for coastal California considering that it evolved with other very familiar mainland native plant species such as Monterey pine, Manzanita and Toyon, hence its 'native-ness'.
I think it's a wonderful way to think about this palm species.