This is a really great little video (with references!). The article seems to acknowledge this evolutionary path when it says "Billions of years ago, another a

This is a really great little video (with references!). The article seems to acknowledge this evolutionary path when it says "Billions of years ago, another ancient cyanobacteria was engulfed and “domesticated” by an ancestor of plants. It shed most of the genes it needed for an independent existence and became what we now know as the chloroplast. In return for a safe environment, these chloroplasts performed photosynthesis for their hosts, fueling a new form of life that eventually spread over much of the Earth." This seems to be talking about the same hypothesis, but I'm not enough of a biologist to be sure.