The 3x the article states means total retirement savings. 401k included. I really hope you know more than a few people with 300k in 401k if they earn 100k/year.
I'm not sure what others have saved in theirs, but in my case, it was more like $200,000 in my 401k when I got divorced at age 40. I didn't always earn the same income as I do now, and also had times where I have needed to decrease my contributions, etc.
(Or I'm in total denial. That's a real possibility as well).