If it’s by choice, nothing of course.

If it’s due to housing unaffordability, that’s an issue

I don’t think there’s anything wrong with living with your folks. Depending on cultural norms it could be indicative of other problems though. Like if most young adults would rather move out but can’t due to lack of jobs, housing affordability or other things. My layman’s take is that by itself it’s not really a problem or actionable thing on its own but could signal some more research needs to be done to figure out whether it’s a problem and how to tackle it if so.

In terms of the article it seems to indicate that it’s a big cultural shift, so naively as someone living on the other side of the world it sounds like it’s worth investigating.