I see it differently. I think RSE approaches their development of all their country-specific guidebooks as an introduction to a country. That is, if you were a first time American traveler to that country (with a short time and modest budget), what are the places most likely to be of interest and worth a visit. Other guides try to be more comprehensive and probably more valuable to someone with multiple visits to a country.
Most of the people I've encountered on tours, signed up without familiarity with the books or the TV show - just word of mouth. Heck many dont even bother to read the book they get with the tour. It's not intended to discourage people from going off their itinerary. More of encouraging people to come back and travel more extensively and independently now that they've seen the minimum. A thousand page guidebook of any country would not be a useful tool.
And what I've heard RS say, on TV, radio, and in person, is that his goal is to encourage people to learn the skills to travel independently. He developed the books as giveaways for people who were already signed up for his tours, but they became so popular that he started selling them on their own. The tours started out as very basic and even spartan, and gradually morphed into something more appealing to a bigger market.