Yeah, exactly. It’s fine to read this study as “people with access to the internet are going to be happier than people without access,” because “without access” is shorthand for a whole bunch of other stuff.
It’s not ok to read this study as “going on the internet makes you happier.” The study doesn’t say that.
That’s why I don’t like the framing as “as happy as a walk in the woods.” Walking in the woods is a specific behavioral choice you can make that affects happiness. “Access to the internet” is not a behavioral choice you can make.
What if I said “being born with access to clean water makes you even happier than a walk in the woods?” It’s a category error.