While the article's conceit that free time has more potential to make you happy when it's free time you can spend with your friends is not untrue, I think it's

While the article's conceit that free time has more potential to make you happy when it's free time you can spend with your friends is not untrue, I think it's pretty obvious that people who are working fewer hours have more chances for their free time to intersect with their friends. If you and all your friends work 20 hours a week, but some of them have firm schedules where they're in the workplace 4h every weekday, while others are in the workplace for 8h two days and sporadic appearances the rest of the week, and whatever other configuration of that you can think of, you are all still going to have a generally higher chance of finding time to spend with each other than if you're all spending 60h working three part time jobs to make ends meet!