For regular workouts there is information on the benefits and importance of doing pull-ups regularly. CrossFit even mentions it in this article. Men's Health even talks about this in one of their blogs/articles.
CrossFit Pull-ups looks like they use kipping (where you using a forceful initial leg movement for momentum which looks like swinging).
As a physical therapist and a strength coach, I do not encourage the violent movement from the Kipping Pull-ups exercise. I've treated many patients over the years with Upper Trap Strain and Shoulder Injury as a result from doing the Kipping Pull-ups from CrossFit.
Why do Kipping Pull-ups in the first place? Also, if you are a CrossFit lover or a Certified CrossFit Trainer, how should I approach you without you thinking that I'm against CrossFit philosophy?