Granted it was 3 decades ago, but when I was in grad school, choosing to use LaTeX seemed to add a few months of effort to the "writing" stage of a thesis. However, it was hard to assign root cause because LaTeX and Word were producing different things. The best technology allowed you to create more, but at a price. Typeset dissertations were beautiful, mine was not.

What LaTeX allowed you to do, in principle, was to "build" your document, i.e., type a single command and have camera ready output roll out of the laser printer. Using Word (or even more primitive tools -- I was on a MS-DOS machine), always required some manual intervention. My workflow involved scissors, glue, scotch tape, and a copy machine. But I got done very quickly once I was ready to start writing.

LaTeX has the massive (!!1) advantage of being trivial to put into version control.

I wonder how they incorporated that into their productivity metrics

As an aside, I have used a workflow where I give someone a a paper to review as an overleaf project, they make all their changes, and then I merge it back into my work picking and choosing the bits I want. And this all works fairly nicely since overleaf has support for git.

There are a lot of problems with that article. See https://news.ycombinator.com/item?id=8797002 for a discussion.