very few can do 12 bodybuilding style pullups thatd be effetive on the back muscles.
swing ups ,yah, but that does fuck all for back development.
dont fool yourselves a back which can do 12 perfect rom slow all time tension pullups is gonna look very good.
that, or as mentioned, when one has sticks for legs, but even then,very hard.
for reference what cswol did for pullup was a disgrace, that was not 1 proper rep.