The straightforward answer would be that when Bill C-10 comes into effect, persons convicted of sexual offences against minors would become ineligible for a record suspension, completely, so there would be no need to have this small subsection of historical offences still referenced in the schedule.
It will become moot at that point once the bill comes into effect, simply because if you're not eligible to obtain a pardon for a child sex offence, there is no need for a further reference in the schedule to those historical offences that are still on the record.