We have a GÜ, not a GU.
Doesn't matter anyway. Then he simply doesn't have his own construction company. But he "builds" the house for you from one source (with the companies he engaged).
The consumer advice center is supposed to check that. They also noted that it is only an LV, not a real construction and service description.
Sure. In the best case, a trained office clerk checks, based on a checklist and sample construction and service descriptions, whether all items are included. The item "windows with glazing according to the current building energy act" gets a checkmark—even if windows with double glazing and catastrophic sound insulation, manufactured in the hinterland of Congo, are installed. There is no actual technical examination or specific consideration of quality.
This is assembly line work at the consumer advice center, no more and no less. Individuality cannot be provided—and it is not even the aim. The service of the consumer advice center is okay for what they do. But not for you.