Yes if the smaller flash is significantly smaller. Fill light generally in the opposite direction and fill in the shadow of the main and thus doesn't really contribute much to the main exposure. However in this case, the 2 flashes are in exactly the same position and the smaller flash isn't that much smaller than the larger flash. As you can see with the larger flash alone it's f/6.4 and with the smaller flash it's f/7.8. A differenet of 0.57 stop.