I think there’s more to this trend than the author’s thesis. Specifically, economic success.
Why strive so hard to pay the psychological price for adulthood if success through everlasting childhood is all but guaranteed? Isn’t this a virtual inevitability of success, that the population will find some kind of equilibrium between progress and self sacrifice? When the vast majority can drift through 12-16 years of school and a light career on into a nice home, family and leisure, I’d be surprised if most didn’t refuse to grow up.
I take it a step further and propose that most adult children know vaguely what they’re doing and seek out others that are doing the same - kind of an unspoken understanding.