It looks like it has much more to do with distractions and content type than the quality of the screens or fonts. From that, I assume that reading a good book on a digital screen with notifications off would show very little difference in comprehension. So, as usual with studies, the article title is a little misleading.
Data involved 469,564 participants from studies published between 2000 and 2022.
So, a significant part of these studies were done before decent screens were even available.
Screens are very very likely irrelevant, they did not control at all for content of the text. It's so incredibly logical that reading a full book gives better reading comprehension than reading tweets/reddit/tumblr/4chan to the point that this study is just one of the "duh" studies that may be necessary to say "yeah we already knew that but now it's confirmed"
Or dark mode adoption.
Book reader community.