Yeah bcs for me it seems like the exchanges are having mostly one big adress where they are storing all the tokens.
I've seen it after large ICO where for example you could simply see 20% LISK being on Poloniex as it was simply one adress.
But it seems with the "pay in" adresses there is a difference.
Yes, that is right, so it is impossible to know the owner of one address in the exchange platform, but I think with some technical help from the exchange, you may do that since almost all the accounts are certified, but I do not think the platform will offer that help.