Plants become listed due to political boundaries. Gentiana newberryi grows nearby, and is threatened in Oregon. It's northern most sighting is within a half hours drive. There you can see people play football on it, run horses on it, pick its beautiful flowers only to find they wilt immediately, and then the flowers end up on the ground. Sometimes hundreds of them.
Elk graze it heavily.
It isn't a sensitive plant, and it's population is healthy and stable in California, but the population happens to cross over to Oregon where there isn't that many stands. Thus it receives the same protection as the truly rare plant. Southern Oregon has many of these kinds of listed plants. There has to be a perceivable threat to the plant population in order for it to be listed. Sometimes the threat is obvious, and sometimes the threat is obscure.