The study unfortunately looks only at individual productivity, not any org gains, and the big claim in the PDF is that adopters "merge roughly 24% more pull requests" over a four month period. not exactly headline-making material. There's no data in the paper whether those 24% extra pull requests actually added anything more valuable or not.
24% of increased productivity (yes, this is assuming of course that the “proxy” of merged PRs reflects productivity) is actually a pretty big deal. Given the salary of developers, this translates to tens of thousands of dollars per year, per developer. My guess is they used # of PRs as a measure as it’s easy to obtain, while other measures are hard, may be due to other factors, etc. FWIW I saw a similar number for my…
[0] https://static.ma.nu/publications/images/2013.07.12_new_york...
[1] https://newsletter.pragmaticengineer.com/i/138252015/drawing...