This reasoning is suspect: repeatedly pushing oneself to work to exhaustion as a form of training for real work where you need to work longs seems unlikely to offer more than diminishing returns. How often do bankers need to work three straight day and nights? Are you positing a physiological process where the more "three nighters" one does the stronger you get?

It seems more likely that the treatment of interns is an expression of sublimated rage on the part of their supervisors. But I suppose they can laugh all the way to the bank.