Lets do a fun experiment.
Here is a video of Matt Kroczaleski doing 30 rep chins. Give it a watch.
Now, read the comments.
(Yes, I realize forcing someone to read youtube comments can be considered cruel and unusual punishment in some states, but stick with me, this is for science)
Look at how many of these comments talk about how Kroc's chins "don't count". He has violated the rules of the event, and got 3 reds. Matt was most likely having an off day, as he's usually a very strong performer.
Wanna see this again? Here is Konstantin Konstantinovs doing 55 pull ups.
If you are having difficulty understanding the comments in the youtube video, it's most likely because they are in Russian. That, or it is because the language skills of many youtubers have rapidly deteriorated and become indecipherable. In either case, they are akin to the Kroc video.
The experiment here? What were your thoughts upon seeing these videos? Were you in the "don't count" camp? Were you wondering how these two got so big and strong with bad form?
Or maybe you thought "so this is how an 800lb deadlifter does chins". Or perhaps "that's what the pull ups of a 900lb deadlifter look like".
This is the difference between the mentality of training and competition, and it is vital that you understand it if you ever hope to succeed in either endeavor. Many times, the downfall of those who do not compete is that they treat every training session like it is a competition, because this is their only competitive outlet available. This means that EVERY movement has rules to follow, and if you don't follow these rules and regulations, your lift "doesn't count". You see this applied to everything from push-ups to pull ups, lunges to crunches, etc to I am terrible with examples.
These rules are always arbitrary and based around some ill-founded notion of what "good form" looks like. The focus isn't on what the movement accomplishes, it's just about what the movement looks like. This is a great idea...in a competition. That is why powerlifting has rules specifically based around how the movement looks, with no concern about what muscles you are recruiting. If you can get your hips below your knees through some sort of sorcery that completely removes your glutes and hams from the lift, you're going to get your whites.
Why the difference? Because the competition is the validation of the training. It is not training in and of itself. No one shows up to a meet hoping to get a good workout in and get stronger, they are there to display strength. So why wouldn't you do this in reverse when you train? Why would you concern yourself with how the movement looks, when you should be concerned instead with what results it produces? If your chins aren't deadhang but your bench and deadlift keep going up, what does it matter? If your squats aren't competition legal in training, but your squat goes up and you never get called for depth in a meet, why should you care? And if physique is your goal, why do you care at ALL about what your lifts look like compared to what they are doing for your body?
The form police are in full force on youtube, and these self important nitwits never have a physique or lifts that are in any way admirable. They just KNOW that they are right, but have nothing to show for it. These are the same people that will come up to you in the gym to tell you that you are going to blow out your knees with your squat style before they waddle their way back to the leg abductor machine for an intense pump. Why would you care about their opinion on anything?
Training is training, and competing is competing. When you are in the gym, you are there to make yourself better OUTSIDE of the gym. If you make training the competition, you will not succeed in either endeavor.