I think they try to stay pretty explicitly neutral about advocating a particular density, it's just that they want people to be realistic about how much a particular kind of development costs. Suburbs are perfectly fine -- but if they were taxed to a degree that reflects their actual infrastructure cost, it would be much more expensive to live in them. There's currently a bizarre pattern where poorer, older, higher-density urban neighborhoods end up subsidizing richer suburbs.

Likewise, it's fine if you want to live out on a farm well away from other people -- but the town shouldn't pay a million dollars to run a paved road and water supply out to your house, when a dirt road and a well is good enough.

The problem is that we all want something for nothing. We all want to live in low-density suburbs like you love, but since charging enough in taxes to pay for them would not be very politically popular, instead we've run up massive infrastructure liabilities, depending on unsustainable exponential growth for funding to fix the old infrastructure.

Would you still love the suburbs as much if your property taxes were 2x or 4x what they are now? If you would still want to live in a suburb, great, no problem. But many people would probably rather choose to move to a denser area and pay a more reasonable tax rate.