You're right—the author doesn't really address this. If a business is unable to price discriminate by adding or removing features, they will end up having to pick either (1) high price or (2) low price. [Stylized example, of course]
If they pick High Price, then they will include lots of features, but only people with a high willingness to pay and high ability to pay will end up purchasing the product. This means that people who would have been willing to purchase the low-end version of the product do not have that option and will instead purchase no product.
If the company picks Low Price, they will not include as many features because (in many cases) there is not sufficient profit incentive. This means that even customers who would have been willing to pay for these features cannot purchase them.
Ultimately, the assumption is that if customers are interested in making a purchase of a "crippled" or "feature-enhanced" product, and the company is willing to make that exchange, then the exchange makes both parties better off. This is what economists call "gains from trade."
Does this mean that everyone customer is better off with price discrimination under every circumstance, or that one cannot imagine a way in which a company could operate altruistically in order to make some customers better off? No. But generally they won't, and this is typically tied to the company's duty to their shareholders. (This is why B-Corps are nice—they give more flexibility in this regard.)