This is the relevant rule -
Les contrôles doivent être judicieusement placés, par exemple aux changements de direction, avec trajet
à peu près direct entre deux contrôles.
almost direct =/= the shortest possible route between controls.
so if the route is 201km, but it is possible to visit the controls in 195km by riding on a 70mph dual carriageway, this would not breach the text your quoted, but would not comply with AUK requirements. So we end up with routes that are often 207km or more, but no extra time for that extra distance under BRM rules because BRMs would not be expected to be significantly over distance.
Indeed you can get from Brest to Rambouillet visiting all the controls in significantly less than 600km (google maps walking), but that doesn't mater as the route is mandatory. Even setting to google maps cycling still comes up under distance. (Rambouilet to Brest would be shorter still due to not needing to visit Dreux (Or Mortagne au Perche))
There is a huge gap between drawing wiggly lines over the map and a rigorous application of shortest possible distance, especially using route measurement by walking which often includes footpaths across fields