It's quite hard to understand your post with fares from PAris to Toulouse but mentioning Melbourne instead of Boston...

Anyway, BSL and MLH are 2 different codes for the same airport "Basel-Mulhouse". This airport is on the French soil but has a Swiss exit. At AF, flights from ORY are ORY-MLH and are considered "pure domestic" (the mileage accrual rate is the one of domestic flights) while flights from CDG are CDG-BSL and are considered "international" (the mileage accrual rate is the one of European flights). And for CDG-BSL, the routing shown is indeed CDG-MLH-BSL with 1 min between MLH & BSL. This is purely artificial and the plane doesn't move at MLH/BSL.