This is not aimed at Apple Stores in particular, it is a universal comment on retail sales people.
I never ask "does it have whatever feature" because the answer will never be no even when it is the correct answer.
Research on the Web is your best defence, but even that is not foolproof. There is an example with the Apple web site in relation to the iPad, though I don't single Apple out on this.
It says that GPS is available on "WiFi + 3G". This can easily be misinterpretted as WiFi & 3G models, especially by European readers. Is this intentional? I think probably not.
It just shows that you purchase a product with certain expectations and find out what you actually got as you explore it's features.
Nine times out of ten, I know more than the sales person in the Apple store. Guess what, I also know more than the car dealers I see. Sales people are not hired for their expertise, but for looks and speaking ability. They also know that their chances to move up are enhanced by how good a job they do at selling. So they do what they think is necessary. I sometimes will help them out when I am in a store playing with the devices. If I see someone that is new to the system is standing next to me, I will give them an honest, but enthusiastic evaluation of what they are looking at. Many customers of my generation get put off by the youngsters technobabble, and hearing from someone closer to their world tell them how simple it is, can be a big help.