Dorian did weighted pull-ups
Maybe at some point early on, but he wasn't doing those once he gained more mass. All this XYZ did pull-ups means nothing. Everyone claims to have done pull-ups.
Franco, Samir and Tony Pearson are all mentioned. What is the common thread? Hint, look down.
The point isn't that you can't get a good back doing chins, it is that your goal is to get a good back, how many chins are irrelevant.