They throw around the word 'analog' a lot, but I'm not seeing how that applies here. Typically, buttons are a digital affair. Do these buttons have continuous states, like a trigger? The article never explains this.
The original Xbox buttons were also pressure sensitive. Developers did not use this feature much, and it was eliminated in the 360 controller. Only a couple of the original Xbox games couldn't be ported to the 360 because of the lack of analog buttons.