I think this issue has a degree validity for those of us who have two passports - provide details of one passport when "registering" and [could be many weeks/months later] then through oversight take a different passport when actually travelling.
I have often wondered what would happen when I travel to the USA if I use one passport at checkin or for ESTA, and then show the other one to the nice man at US immigration upon arrival, but haven't come anywhere near to having the courage to actually try it to see what happens!!!