I've seen the big groups in Singapore.
Where I live I don't see groups doing this much, but I swear in any sizeable park, worldwide, you can find at least one older Chinese woman wearing a visor, doing flappy arm exercises while walking.
When I was young I remember thinking I'd be too embarrassed to do it. Not now though. Now I understand, and I'd be so down for a group version.
They're definitely on to something - mobility for the win.
There's really no anglo version of it, either. Calisthenics, but I never knew many older people who did that.