There is no stop over allowance for TIF policies, including Aggregators.
As long as the customer does not leave the airport and their stopover is 24 hours or under, they will not need to declare their stop-over country.
If for example they are going to Australia but have a stopover in Singapore, where they actually leave the airport, then they will need to have the higher risk destination, i.e. WW Exc as their area of cover.
If they are not leaving the airport at the stopover or/and their stopover is less that 24 hours, then they are fine to have the lower risk destination.