I will also note that all solar science, attempting to predict the life cycles and 'phases' a star goes through in its presumed life span, are all really an accredited form of pseudo science and at best, over-educated guesses, based on results we get in extremely SMALL and extremely SHORT terrestrial experiments. Which are then meant to describe the extremely MASSIVE and extremely LONG-lived phenomena we call stars.
When talking about star life spans, you are talking BILLIONS of years, and tens of thousands of years in between onset and finale of the supposed phases themselves. The scientific method sorta breaks down when the 'Observation' and 'Prediction' portions of it, is the span of HUNDREDS/THOUSANDS of life times.
So the community relies on statistical sampling (we see countless stars), probabilities based on individual element characteristics, and what we find in analyzing the spectrum of light from the variety of stars we can otherwise barely see.
Its tantamount to the early Greek philosophers observing the divisibility of matter and pontificating over Atomism, without ANY way of actually verifying their statements. Sure, they where kind of correct, but LARGELY very mistaken. (Note: I know the Greeks are not the only ones that talked about the idea, but its convenient)