[kinlan]

Good point. In lots of cases these sites are actually doing the detection of the device class on the server and never returning a fully responsive site in the first place. There is certainly a balance to be had on responsive vs adaptive, in this case with this piece of guidance it is to give developers and users the chance to adapt more appropriately to the screen constraints at any time. Min-device-width is pretty much permenant so it is harder to adapt to when the user is on a big screen but only usng half of it.

For most content based sites there is not a huge amount of reason to have drastically different html, CSS or js. For apps we are yet to cover that fully.