Openrouteservice scheint den maxspeed-Werten (70 vs 100) etwas zu viel Relevanz zuzuordnen.

Andere Router machen das besser:

https://www.openstreetmap.org/directions?engine=fossgis_osrm_car&route=48.75566%2C8.34187%3B48.75480%2C8.34246#map=19/48.75523/8.34218&layers=N