Part of the difficulty of enforcement, even if FA are willing and able, is that 3 FA isn't enough to watch over 120 people streaming in, at least not standing at the front door. For Ted flights 1/3 to 1/2 are in E+, so that's a lot of BP if each are checked individually. It seems that FA can spot people coming up from E-, but are unable to see if people simply sit down in a confident manner as they walk down the aisle.
Perhaps if pax are told that they should have BP ready to be checked, and before door is closed when FA do the count, they can announce for all BP to be readied so they can check them :P I would dread this if I am a FA, but it's the only way to truly root 'em out.