Can't speak for Sam's reasons, but the flap lock is just a plastic rod - or at least it is on the Mondy, and looks like it is on the Coug - and can be easily jemmied or snapped through brute force and a screwdriver.
A few years ago we had a spate of Caravan Utilising Nomadic Travelers doing exactly this, then disabling the anti-syphon and nicking the fuel. Our Mondy got done while it was loaned to Ms. Mako's brother. I repaired the flap lock using brass rod that I threaded and drove into the actuator.
Trouble is that although that car wasn't done again, the spate didn't end. People started fitting locking caps. So the thieves just cut through fuel lines or drilled the tank. In a few cases, they just cut the straps and took the whole tank...