This is also covered in the book. North Korea was more prosperous than South Korea until the 70s. But this was solely due to their massive subsidization by China and the Soviet Union, who basically gave them everything from food to industrial equipment to technology.

When the USSR collapsed, and China began to find North Korea an embarrassing crazy neighbor on their border that they wished they could be rid of, the money stopped flowing and that led directly to the famine of the 90s. Meanwhile, South Korea continued to become more democratic and more prosperous.

But you're right that the view the North Koreans have of the world still dates back to the 60s.