He’s saying design should have an aesthetic, so he’s not saying “zero ornamentation above basic function”. Braun radios often had speaker holes in patterns that were chosen mostly to look nice.
If your beautiful desk enhances your surroundings, than it has this function of “enhancing your well-being” (his principle 3). If this aesthetic is best for you, it’s not bad for your life.
But any ornamentation over and above what is pleasing you in this way, is not “good design”, it’s extra, it’s something else.
For instance if your beautiful desk is so beautiful that people stop and stare at it when they enter the room, and you can’t write a letter at it because you can’t catch your breath, well, that means it’s very good at being a showpiece artistic achievement, but it’s not the “best design” for a workspace.
He pushed people to be simpler, as a principle, because people tend to over-flourish, and put hats on things. The hats may be undeniably pretty and exciting, but if they are not meaningfully connected to the actual use, they aren’t as good a design, specifically for the use.
