I can contribute something as a local: I think this is about Mr. and Mrs. Kö*** in the Bien-Zenker representation in Bad K***. They actually seem to be well connected when it comes to plots of land, because they have built 5 houses alone in our development area, and I know the same from other developments in the region.
I would advise against them for other reasons: the houses are planned so poorly on the plots around here that it’s painful. They just slap catalog designs onto the plots for clueless new builders, that you basically have to shake your head at. Impossible orientation, impossible terrain modeling, no consideration of neighboring construction activities... it borders on outrageous. And then people sit in those houses paying a lot, with garages to the south, no living room windows, or views of L-Stein Eiger north faces. If you don’t plan properly yourself (or with help from the forum), you’re betrayed and sold out. Otherwise, Bien-Zenker houses are a matter of taste. You can definitely live in them.