Quite often the training captains/interviewers are trying to work out if you are:-
- the type of person that can think outside of the square
- or only see the obvious
- or jump to conclusions without taking into account all the available information
Bit like the old one about the captain comes down for drinks on a layover in a sparkly dress. The naive amongst us would go "oh jesus the captain is a raving cross dresser I had better stuff some tinfoil down the back of my trousers". The more mature would say that she scrubs up quite well and would pay a gentlemanly compliment.
Same goes for the vodka bottle. You could think of a host of completely innocent scenarios for having a bottle of vodka in your bag. Note that the information given NEVER said it was open or the captain stunk of booze and was half dazed slouched over the controls. I myself had a nice bottle of port in my bag a few weeks ago after I purchased a cheap bottle from the man with a van that drove airside.