You can. And I do. And given your post, I assume you do too.
But did you know that most people don't?
I teach people computer skills (a lot of children, ages 8-12, but other ages as well). Only the very clever ones (those we can expect to welcome on HN in a couple of years ;-) ) figure it out by themselves. You'd be surprised of the in-your-face stuff people simply do not read on the screen. I then point it out, but it's about 50/50 whether they'll pick up the habit.
And it's the same thing with this interface the author has designed. It's all intuitions about how he uses computers, how people like him use computers, and how the self-selected group of feedback-providers use computers. Nothing about the general public. No research, no tests, no reference to classic UX textbooks and theory.
Now if he had stated upfront that those three categories are actually the only intended target audience, then at least he would have acknowledged that this is a possible problem, up-front. Not doing so, it appears he hasn't given much thought to it.
So, sorry but what I see is not a user interaction designer, but a graphics designer with a cute hobby.
If you think that's harsh, imagine he'd have redesigned the user interface of your car. Would you trust the ideas reading only about mockups and "intuitive" justifications? Wouldn't you think, mm-mm yes nice ideas but until you actually tested them on a focus group they could go anywhere and further effort is pretty much wasted until you do. What if you assume his driving style is rather different from yours?
Settings > Keyboard > Shortcuts > Keyboard
Settings > Trackpad > ...
OS X actually allows a lot of customization. You assign a keyboard shortcut to any menu item in System Preferences -> Keyboard -> Shortcuts -> App Shortcuts.
Many of Apple's UI interactions can only be discovered through guesswork or reading the docs. If you open Launchpad often, nothing alerts you to the fact that there's a touchpad gesture for that. Unlabeled icons are rife in iOS and there is no discovery mechanism equivalent to a tooltip.