There are Apple HIG, and then there is MacOS App Store.
Nearly every single interaction is different: a different animation, a different modality, a different way to dismiss and/or navigate. Slide left, a modal in the center of the screen, slide right, a modal at the top of the screen, a modal dims the screen, slide up, a modal doesn't dim the screen, an item in the list gets its own page, an item in the list is displayed as a modal, slide down, there are animations, there are no animations...
Get 15 people, put them in 15 different offices with no communication between them, set them to work on one feature at a time. You will get something very similar to the App Store.