By the docs this function is called in two different scenarios, if a quest is full and receipt redeemers equals the max amount of total participants allowed in the quest - only withdrawFee is called. If a quest doesnt hit the max total participants, first the owner calls the function withdrawRemainingTokens to withdraw the remaining tokens and then the fee should be paid with the function withdrawFee.
Overall the best solution of this problem is that the function withdrawRemainingTokens, both does the withdrawing part to the owner and pays the fee to the protocol as well. This is considered the safest way:
First, if the receipt redeemers are below the totalParticipants, can withdraw the remaining tokens and pay the fee at the same time. Second, if the quest is full and receipt redemeers hits the total amount of people allowed, only the fee will be paid to the protocol and will skip the withdraw remaining rewards part.
