I watch (or listen to) a lot of youtube on my iPad (and sometimes on my TV, but not too often). I wonder if youtube watching is also correlated with the mentioned brain changes.
If it notices you are interested in something, it will show you a glut of content on that particularly subject. Some of the videos are just churning out similar content. If you click on a Monty Python video, Python takes over your suggestions. Nothing against Python, I just want to watch a variety of things.
Science doesn't work by looking at things and saying what's "obvious" or "common sense", because what's supposedly obvious or common sense is often actually false.
Thinking that watching video content on a different box is any different in this context is wishful thinking.
There's more variety of content on youtube, whereas I think TV sometimes caters to lowest common denominator (although that's less the case in the era of streaming: TV is much higher quality than it was when this study started in 1987).
On youtube, you could watch lots of silly dancing videos, car crashes, etc., possibly rotting your brain. Or you could watch history lectures, book reviews, documentaries, etc.