I am not sure if the above statement true. Several good friends of mine who work at BA that this is simply not the case. Although you maybe able to put something on the boarding pass in the information panel (thus in theory fake your status that way), you cannot fake your actual status. Remember that lounge dragons almost always swipe your boarding cards these days and it makes a call to the system and brings up your status there. If you can, have a look at the screen the lounge dragon is looking at after they have swiped your boarding pass.

Remember, when you put your FF number in, it simply puts a call to the foreign carrier's database requesting tier information, and then inserts that data into the booking. This process is done by the database rather than the agent.

BA lounge dragons are simply wary needlessly. A simple swipe of the boarding pass is all one needs to check.

Where information can be often wrong is when you go up a tier, but the system has not yet updated as it has not polled the foreign database. The simple way to fix this is to ask the agent to delete your FF details and then reinsert them into the system. Almost always does this trick unless old info is still lying in a cache somewhere.