I understand your objection, but perhaps what he is saying will make more sense with a little background. It's not that these youth are people between jobs at startups, which is what this community might have in mind when hearing about someone who lives with their parents. There is an ever increasing number of Japanese youth who choose not to obtain full time employment, who work multiple part time jobs, and who do not amass any savings. It's not necessarily that they are not saving money because they aren't making enough; rather, they are spending all of it on non-essential material goods -- be it clothes or technology or collectible figures or any other such thing.

As far as I understand, this is a "live for now" cultural reaction against the failure of the salaried worker lifestyle that existed prior to the Lost Decade(s). It was once the norm for a Japanese student to graduate college and to then work for one company for the rest of their life. This was known as being a "salaryman". When Japan entered this long recession, many young people saw that their parents had worked so hard for a promise that couldn't be fulfilled. They rejected the salaryman lifestyle for the sake of a less stressful, less structured lifestyle focused more on cultural identity, such as style, music, a hobby, etc.

Sometimes such youth do move out (such as living with a partner -- marriage is becoming increasingly delayed though) but I think that the criticism is that this lifestyle is just the pendulum swung fully the other way: it is too focused on the immediate future and lacks any long term planning. A person in this situation will have a difficult time dealing with a family emergency, whether it is a sick parent or a pregnant girlfriend, for instance.