They are considering that once you have loaded a round into the chamber, all you have to do fire the gun is pull the trigger. That is how double action guns work, thus the name. Some gun manufacturers will be more specific (and accurate, though potentially misleading), to call them what they really are, technically, but then gun buyers often get confused as to what the real difference is. So, S&W calls them 'double action' for simplicity and so as not to confuse gun buyers. M&P's are great guns.

Nope! This pistol falls under the striker fire class. Thusly it does not possess the actual hammer and therefore should only be considered a "single action" as the action cannot be manipulated like that of a 1911, m9, or cz75. But it is an awesome pistol either way :)
Pistols i own chiappa m9(.40 cal), sw40ve, Russian Makorov 9x18mm

Looks like you are right. It has a 5" barrel. It does have the adjustable trigger stop and the enhanced trigger. It is Single action. Good catches. This is a pretty sweet pistol and looks to be a pretty sweet deal too! If you decide to get it post a review. I'd like to hear how it works for you. Happy Shooting!