I just have to say WOW. The fastest way to tear your rotator cuff is going to failure into a dead hang? Really? Let's look at the two exercises and the motion your body is going through.
Strict pull up starting from a dead hang- your shoulders are feeling tension through out the lift, as you go up and down. Which is safe. The muscles that will fail first is most likely your grip/forearm/biceps. Yours shoulder is used as a supporting muscle through out the lift. This is safe. (Some people have pre existing shoulder injuries that they may or may not know about, due to muscle/strength imbalance from front delt to rear delt)
Kipping/butterfly technique - at a dead hang your shoulders are under tension. As you swing your lower half forward there is still tension on your shoulders. As your momentum carries your bottom half back is takes away tension in your shoulders for a brief moment. Your body acts like a pendulum moving around your shoulders. After your momentum stops, all that tension is slammed back into your shoulders. Not good. Compounded with 100 rep workouts youll pay the price when your older.
Kipping is a gymnast movement, but do you know why they do them? Do you think they actually train kipping and other half ass pull ups? Kipping is a basic movement for gymnast to get up and over without burning too much energy, so they can have more energy to complete their acrobatic act. Gymnasts may practice a little of kipping for form so they don't burn unnecessary energy but they actually strength train as in do real pull-ups and other strength routines. Kipping would be considered an explosive movement. By that definition there is no need to take an explosive movement for insane reps and is potentially harmful. The same for snatches and cleans.
There are other/better ways to build muscle endurance instead of thinking crossfit has reinvented fitness. The problem is a majority of the gym population have overinflated egos and don't have a clue how to achieve what they want. which is why they see very little gains if any. Some people don't want to learn and rather have someone else tell them what to do. The finess industry has been a financial pitiful as there is really nothing new when it comes to strength,endurance,cardio,etc for personal fitness trainers (not to be confused with strength and conditioning coaches people who actually have credentials in doing what they do. Atleast a cscs certification. Not crossfit certified or whatever other minor cert their is out there). Crossfit gives them a bigger profit for sure. Ill leave it at that, feel like I'm writing a freakin novel on my phone.
One thing to add, I would consider to do a wod as a see how i stand and amongst friends. It would be a dick measuring contest sorta like "hey how much you bench" type of thing

. But I wouldn't train like a crossfitter.