As the title says, ways that would normally not be accessible by vehicles but are tagged as vehicle=destination in OSM are not incorporated into routes, while they should be. In the following example part of the W. Göttelaan has this tag combined with highway=footway: RouteXL - fastest route with multiple stops.
This is probably also the case for keys of more specific transportation types such as motor_vehicle and motorcar, but I do not know of any such cases in OSM.