My sentiments aside, I'd like to know if it will actually help, and if my ebook reader (which doesn't scroll) is actually okay. So, looks like they could have extracted more knowledge here...

I don't think anyone is confused whether hiking or doomscrolling is better for you.

But to understand the mechanism behind the claim in the title it would be useful to know whether social media plays a role here, or if it's continuous scrolling, or something entirely different. Understanding that might not make people go outside more, but it would help make the things people are already doing less harmful.