The author's description of her symptoms match pretty strongly to my experience of depression (I would say they match my experience when I'm at my "neutral baseline" - definitely not in my worse moments). From what she's describing it doesn't sound like chronic depression but more circumstantial. But it's definitely depression. She doesn't need to have a badge of "I've had this for 20 years" to have a perfectly valid, and tough experience of depression.
She clearly went into it with already established patterns like exercise and a high degree of self awareness, which has served her well during this period and allowed her to move forwards through it. Some of the ideas she talked about were extremely interesting to me too. I've been trying different things for decades and yet there were still a couple of new ideas here that I haven't considered before.
For people experiencing depression over a longer timeframe, the experience may be different. But neither experience is invalid, nor invalidates the other.
Hope you continue to push through your bipolar! I've been told my depression is "mildly bipolar" whatever that means, but I definitely don't experience the extreme swings on a regular basis that are typically described in relation to bipolar.