I guess I have to be the guy who stops the music once again. The answer is, “No”. Оne arm pull-ups/chin-ups do not equal balloon sized biceps. The evidence is everywhere. There are plenty of people on YouTube who can do one arm pull-ups easily without exceptionally big biceps. Rock climbers are a good example.
Why? First, the majority of people into calisthenics are natural. This limits the potential for growth right from the start. Second, the nature of the movement requires you to remain somewhat light. Having extra size on you helps your squat but kills your one arm pull-up.
Back in the day, I read online that if you can do 15 one arm pull-ups, you have most likely reached the size potential of your biceps. Whoever is the genius behind this statement, he is wrong. First, setting arbitrary numbers is not logical. What if I can do “only” 10 one arm pull-ups? Does this mean that if I add 5 more, my arms will get bigger? No. Arbitrary numbers rarely work past a certain threshold.
Nevertheless, you can definitely reach your bicep potential through heavy pull-ups/chin-ups/rope climbing. Pulling in all of its forms will always be a great upper arm exercise – way more fun than curls, although I like those too.
At the end of the day, genetics will dictate the name of the game. For example, if a classic fragile ectomorph trains intelligently for a long time, he will get to that mystic one arm pull-up one day, but this does not guarantee growth beyond what his poor genetics had ordered. Training does not change your genes.
It’s also worth mentioning that the world of street fitness has been infiltrated by fake natties. People wrongfully assume that if someone is doing push-ups in the park, he must be a “full natty brah” by default.
I am almost sorry to inform you that many of the street fitness celebrities are on steroids. Sorry, but this is the truth. I really don’t care if the bodyweight purists out there feel offended. When you are 200lbs/90kg of muscle with bitch tits, you are not natural regardless of the exercises you are doing. Do you remember the video of the homeless bodybuilder from France? The guy wasn’t natty either. Angles are everything. The media know it very well.
In brief, the one arm pull-up is worth pursuing if you like the movement. Still, you shouldn’t expect to develop 18-inch shredded arms from it. It’s not going to happen unless you are a mutant, to begin with. Moreover, you don’t need one arm pull-ups to reach your arm potential. You can use other exercises too. The goal is to progress and get stronger through consistent training and intelligent programming that respects the cyclical nature of strength gains. The means of transportation (exercises) are entirely up to you.