I would concur in general. You trim the horse to anatomical correctness* and protect the trim with a shoe, if required. But even in this there can be deviations from strict compliance with the anatomical correctness standard if the environment in which the horse kept requires same. In terms of differential climates in Germany the “delta” will be pretty small. In North America you can go from the Arctic to the near Equatorial, and from tropical rain forest to desert. Within such a wide range of environments there can be a fairly wide range of potential practices. The danger comes when someone decides that the rules appropriate to their local circumstances are really Rules of the Universe and demand that everyone follow them at all times, everywhere. The “barefoot” folks are particularly bad about this.
You have to care for and ride the horse in front of you, not the one in a book, video, or movie. You CAN define standards within broad guidelines but you still have deal with what you have, not what you wish you had. Or “identify” that you have.
G.
*By “anatomical correctness” I mean the conformation of the horse you’re working with, not a “perfect” horse. I like your statement, “The farrier’s job is to make it easy for the horse to move in comfort, not to help owners indulge in fads (see my second sentence!!).” It sums up the matter rather well.