The charge that applies to exports from Atlantic Canada is payable only in circumstances that have been established in the softwood lumber agreement, which are faithfully reproduced in the implemented legislation. So it's necessary for Canada to be able to meet its obligations to begin collecting possible charges on exports from Atlantic Canada before the legislation receives royal assent.
Thus, the possible charge applicable to Atlantic exports must be structured as a charge so that Canada can meet its obligations.
If the charge on Atlantic exports were structured as a penalty, Canada would not be able to meet its obligations in that regard.