They address that in the new macOS 11 HIG [1], indicating that protrusions from the square look "to combine depictions of the physical objects that best convey

They address that in the new macOS 11 HIG [1], indicating that protrusions from the square look "to combine depictions of the physical objects that best convey the app’s core purpose" are acceptable. TextEdit, Preview and Xcode all have elements sticking out a bit. [1]: https://developer.apple.com/design/human-interface-guidelines/macos/overview/whats-new-in-macos/ https://developer.apple.com/design/human-interface-guideline... That said, I still think overall it's a loss in terms of usability. (I find that without shape to distinguish icons on iOS, I often confuse icons that are broadly similar in color when I'm not paying attention, even though the images inside the roundrects are different. I can't be the only one.)