Big companies tend to develop cult dynamics. This is not an exaggeration, but a consequence of how humans tend to operate in large amounts. And I'd wager that in the case of Silicon Valley tech companies, this is also something that they embrace and nurture. I don't think this is a controversial take at all, and rather obvious.

She was probably not "afraid of being let go" (fired), but had convinced herself that it was of the utmost importance to have this level of committment. The book probably reads similar to those books of someone who leaves their church or cult.