In the iPhone or iMac, what's on the screen is what is important. Nothing else is important, so it's not there. One of Rams' principles: "Good design is as little design as possible."
Contrast that to a competing product like the ASUS ROG Phone: RGB lights, not-strictly-necessary cosmetic vents, asymmetrical lines, printed design patterns. Now THAT is a product that would make Dieter Rams throw up in his mouth!
I actually agree wholeheartedly. Apple's devices are the apex of form following function, which is why their form advances so rarely: the functionality of the iPhone changes so little from year-to-year, that Apple doesn't really need to re-engineer much. Hell, the iPhone 12 is just a redux of the iPhone 5 footprint, an anachronism that's yet another great example of form meandering while function stagnates. The deficiencies in our current devices are clear: they're centralized, non-extensible, and exceptionally difficult to fix when they break. Apple profits off all three of those markets, so I have little faith that they intend to change anything there soon.
> Contrast that to a competing product like the ASUS ROG Phone
Don't make me (or Tim Cook, for that matter) laugh. The iPhone doesn't compete with the ROG Phone: they're ostentatiously different products. One is a gaming phone, the other is an iPhone. You're comparing a dune-buggy to a Ford Fiesta, which you're welcome to do, but will sway very few of their respective audiences.