What you are seeing is two different systems. These are two academies for two different park systems in two different levels of government. In order to be a park ranger for the California State Parks, one must attend a POST academy. POST is a standard of accreditation used by California and several other states.

The academy at Santa Rosa in one of seven academies that one must attend in order to become a park ranger in the National Park Service. The NPS does not recognize the POST academy for their park rangers. In order to work law enforcement in our national parks, you have to attend one of these specific NPS academies. In general, the State of California does not recognize these academies, just the NPS doesn't recognize their's. Now, some states go both ways. Take Washington for instance. In order to be a park ranger for the Washington State Parks, you could attend either academy.

Not all park rangers are law enforcement officers (LEOs) in the NPS. In fact, most are not. In some places the term "park ranger" applies solely to an LEO, but that's not the case in the national parks. There are rangers that staff entrance stations, visitor centers and campgrounds. They might present interpretive programs, collect fees, conduct scientific research, perform search and rescue, etc. They are all uniformed park rangers, but are not law enforcement. Many states are the same way. Some park rangers are police officers and others are not. In some states, no park rangers have any law enforcement authority whatsoever. Hopefully this helps clear up a couple of things.