Most of this line length theory isn't backed up by any science. Newspapers are a particularly poor example as their line lengths are typically much too short to

Most of this line length theory isn't backed up by any science. Newspapers are a particularly poor example as their line lengths are typically much too short to provide "good" readability. It's also worth noting that newspapers traditionally used columns because they allow individual articles to be typeset and then divided into pieces later during composition. Not because they offer some kind of readability advantage.