> “The purpose of visual consistency is to construct a believable environment for users… The transfer of skills is one of the most important benefits of a consistent interface, especially for beginning users.” pg. 10

> “…consistency makes it easier for a user to learn new applications; it also makes it less likely that a user who follows habits learned from one application will make a disastrous mistake when using a different one.” pg. xi

The HIG goes beyond simply expressing principles of what makes for a good UI. The consistency in and of itself allows users to develop an intuition and muscle memory for how their computer will work. That intuition is destroyed when different apps look and behave differently. In that sense, it's better to be less intuitive according to some abstract principle if necessary to achieve consistency. It will take the user longer to understand a "more intuitive" UI starting from first principles than to understand a UI that exhibits the quirks embedded in the HIG they already know.