I understand that point, and to rephrase my objection, I am concerned that people are accidentally trading long term choice for short term choice. There are many aspects of living within one's means that are out of the control of the individual.

For example, if a young person retired 20 years ago, he probably would have done a poor job budgeting for increases in prices for healthcare, especially given what the individual market looks these days. If, after a twenty year absence from the workforce, he is forced to work again, he will rapidly be approaching traditional retirement age with a large gap in work history and limited career options.

Maybe working or volunteering on the side can keep his skills sharp, but how easy will it be to convince potential employers of that fact?

It's possible that people are saying "retirement" when they mean "frequent sabbaticals", in which case, some better labeling of that lifestyle choice would clear up my confusion. Even then, I wouldn't blame a potential employer for being wary to give challenging job openings to sabbatical-takers due to the higher risk that they'll take off.