I suppose with the relaxing of customs rules this practice has been discontinued.

On one of my flights I took a several years ago AI had the domestic and international passengers segregated in the cabin with flight attendants making sure there was no crossover by passengers between the sections. This was done to prevent international passengers from bringing in contraband items by handing them over to domestic passengers. There was a sign at the divider to let passengers know which section was for domestic and which was for international transit passengers.