The bit of the sentance you stripped out was the bit where they emphasised that they were describing a basic and simplified definition because there is actually an entire chapter on what you are talking about - i.e. consumer preferences and different considerations for different models (including "What does the customer perceive it as fair/value when considering SaaS vs perpetual licencing?").
Sometimes you start with overly simplified concepts to help people frame/grasp later ones, i.e. when teaching a child science it's better to teach them that there are 4 fundamental states of matter first, before they later learn that there are 29 known including the Bose–Einstein condensate, Fermionic condensate and Rydberg molecule.
Atoms don't look like the stereotypical depiction. I remember in my high school chemistry class, our teacher specifically said that atoms were not like this but for teaching at our level, it was fine, but to know that orbits are not like this.
I feel it is crucial that teachers explicitely add the caveat that the explanation is a simplification. It's a whole lot easier to add new info if you know things area simplification, rather than a cast in stone model.
Sometimes you start with overly simplified concepts to help people frame/grasp later ones, i.e. when teaching a child science it's better to teach them that there are 4 fundamental states of matter first, before they later learn that there are 29 known including the Bose–Einstein condensate, Fermionic condensate and Rydberg molecule.