It sounds like BS in my experience but the actual quote says: "We show that LaTeX users were slower than Word users, wrote less text in the same amount of time, and produced more typesetting, orthographical, grammatical, and formatting errors. On most measures, expert LaTeX users performed even worse than novice Word users." https://journals.plos.org/plosone/article?id=10.1371%2Fjourn...
According to the data mentioned in "Equation Text" part, their abstract is misleading at best or just wrong (it seems we can't rely on authors to summarize their own papers accurately)