Most likely, that shade of grey was chosen precisely because the section headline is black. If both were black, it would compete with the typographic hierarchy,

Most likely, that shade of grey was chosen precisely because the section headline is black. If both were black, it would compete with the typographic hierarchy, making it distracting to skim the entire page. Good design is a form of engineering. You have a set of principles and successful patterns– such as the ones on the linked page– but your job is adapting to real world constraints. In this case, the challenge is making a headline look like a headline only relative to the example, not the page. As far as the Safari tab shortcut, that's consistent with the rest of OS X. How did they originally arrive at that shortcut? They probably tried several combination, all within reach of the home keys, and that felt most right. Why include the power switch on the keyboard? I know every user's first question is "where is the on switch?" and that position seems highly visible, and it can be consistent across all macs. In my entire history of using Macs, I've never had an issue cleaning the power key. No idea why they made the displays more reflective. But given their overall attention to detail, a lot of thought probably went into it.