The mark does lose.
You cannot dispute atm charges like credit card charges. Your liability can be limited if the card is promptly reported lost or stolen, but since the real prize is not the amount withdrawn but the acct. number and pin to victims bank account, I suspect the con man suggests that they dispute the charge on the next statement.

The money they give back to the mark is his own.
It seems like money, but it is really the bundle of newspaper wrapped in a handkerchief.