Back in the aftermath of the Bali Bombing Garuda were routinely flying with twenty or fewer pax. Several flights had more crew than passengers.
I don't know the actual rule, but there would be very few international flights or non-peak hour domestic flights leave the ground if they needed a full load. I haven't seen the load numbers recently but Tiger don't always look full to me when they arrive/depart.
Maybe he was mistaken? I wouldn't be surprised if they had a break-even number, but full or nothing seems a bit unrealistic.