Some of my female coworkers have confirmed this to be true. They say younger guys have problems finding a girlfriend, because they expect her to take care of him the same way his mother did, and younger Japanese women don't want to put up with that kind of attitude anymore.
Regarding social development, my feeling is that Japan is one or two generations behind Western countries.
This is rampantly common in (esp. Southern) Europe as well. The stereotype of the Italian or Greek "mama's boy" who can't do anything around the house and expects their SO to be their surrogate mother is very real.
I really don't think you should be using this as evidence to paint Japan as developmentally retarded as compared to "Western" countries. Respectfully, it comes off as parochial if I'm being charitable, or as working backwards from a desired conclusion if I'm not.
Moreover, this is a trend that crops up all around the world, not just in Japan or Europe. There are plenty of people like this in the US as well. I've met several grown men with well paying jobs who eat out for every meal and have their mothers do their laundry every weekend.
When I say Japan looks to me to be one or two generations behind, is because some of the things I see or hear here are the kind of situations my parents or grandparents got to experience when they were young. Not only what we already discussed, look also at the situation of women in the workplace, or LGBT rights.
There are a great many “western” countries where this is even worse than Japan including the one so often named the primordial “western” country.
I have no idea idea why so often when Japanese culture specifically is discussed the idea is sooner or later proffered that there is some homogeneous “western” culture with common elements that supposedly exists. It certainly doesn't seem to rise when, say, Russian, or Indian culture is discussed.
The classic book on the subject is "The Anatomy of Dependence" https://en.wikipedia.org/wiki/The_Anatomy_of_Dependence
The gist of this is that the parent-child relationship is the ideal one and that extends into the relationships in a collectivist society including that of a manager to an employee.
And so the doting mother to her child... extends a bit longer. The doting mother part isn't new - but rather that that relationship is seen as the ideal one... gets into cultural comparisons.
... but that's the word that can set you on the search for understanding of that phenomena.
It was said that their mothers do everything for them and for a much longer time than other countries. Is this true?