The fact that Jean Prouvé built this prototype in Saarland is probably due to the fact that Saarland was under French protectorate after the war and Jean Prouvé was on friendly terms with the military government of the Saar region.  Furthermore, he was friends with several architects working in the Saarland.

In June 1946, against the background of the lack of housing after the war, the plan was made to build a settlement of 137 prefabricated houses in Neunkirchen (Saar)….

MORE under:    https://kreutzer-modern.de/jean-prouve/