'iOS 7 introduced a much more complex physical language while stripping out many of the visual cues that developers had relied on to instruct users.
Like what? I don't have an iOS device, so I'm not really sure what they're talking about.
I'm not sure what "physical language" means in terms of a none physical medium such as software but if I had to venture a guess I would say they are talking about the new "flat" design where buttons and such are not raised but simply look like hyperlinks on web pages. On top of that the previous way you access spotlight is gone, no longer to the far left screen but brought down from the top view swiping in the middle of the screen, while swiping from the top down brings down notifications and swiping up from the bottom brings up some default apps like the calculator and music controls etc.
It's rather confusing to tell some to swipe down to access notifications, only for them to end up in spotlight because they didn't swipe down from far enough up on the screen. Plus there literally is no "visual cue" for any of this swiping. Most people don't even know this shit exists.