The quality assertions are the most defensible empirically. I wrote the post at the office away from my bookshelf which was the main thing keeping me from including them up front (flicking through my old copy of code complete now). Capers Jones' "Software Defect-Removal Efficiency" (https://ieeexplore.ieee.org/document/488361/) would be the main one on the effectiveness rate of code inspections. I've collected a few other relevant papers over at https://github.com/joho/awesome-code-review
The second two themes around education and culture come more from my personal perspective and experience - largely from running the engineering teams at Envato and 99designs respectively. My feeling is the educational and safety elements of code review have come up online a lot more over the past couple of years - but that's just my anecdotal view.