You're right, no trials on methodology that resemble something like clinical trials. And of course the reason for that is it would be incredibly expensive to even run a reasonable pilot (two small teams head to head implementing a realistic system), and if any organization has actually gathered data, it would be the crown jewel of proprietary knowledge. Not something you would ever open source.
The only thing I can say is that an immature field is one with opportunities left. If you can figure out how to jump the hurdles you can make a huge impact.
PS, an example of a bug study like I mentioned (this isn't even that great but just goes to show how hard any sort of software study is): https://www.google.com/amp/s/blog.acolyer.org/2018/06/28/how...
FYI for others wondering about the same, I wouldn't wait the full 10 years unless you are going to study something very industry adjacent like software engineering methodology. I've had to spend a lot of time relearning anything theoretical.
I bet the sweet spot is 2-5 years.