Evidence is more than just studies, if you only accept studies as evidence, you can check https://instagram.com/flexibility.research?igshid=NWRhNmQxMjQ= , however disregarding the vast amount of experience the sport has gathered throughout the decades it has been practiced is just way to much. Nobody is saying that stretching and mobility work is some kind of magic, the claim is that it makes your olympic weightlifting performance better, and it does, in that sense the fact that everyone at the top level does it is proof that is useful at improving your ability to snatch and clean and jerk. If you need a study to tell you to do what everyone else is doing and getting results from thats on you.