I can't speak to the rigor/validity of this study, but, taken together, the benefits of exercise are amazing. If exercise was a drug, no one would believe all the benefits could be real.
I think it's not the benefits we get from doing it that are amazing. I believe it's because we are supposed to normally feel great most of the time, but NOT doing those things that should be part of a regular human life is having terrible effects on us.
If suddenly we do right by our body, it functions correctly, and the relative difference is so huge we perceive that big gap as a fantastic gain.
Like when a head/stomach ache goes away, or when you finally have time to rest after a hard week, and you suddently feel so fresh. But that impression is what should be normal.
My health always deteriorates when I'm more social.
Social activities rarely complement healthy sleeping and/or eating habits, in my experience.
There was a science fiction story I read once where the main character would get into an "exercise box" where all his muscles were stimulated and he came out well-muscled and fit. There was also some twist where he either couldn't afford or didn't have time to be put to sleep, so he had to endure all the pain.
(can't remember what series it was)