Hi Mikey - this is one of my local roads! I think this was better as it was previously, to be honest. Motor vehicles are not forbidden from using the road (and in fact they do use it - it's popular for people driving to do a walk around Ditchley) so motor_vehicle=no is inappropriate. There is a legacy "Unsuitable for motor vehicles" sign, which dates from before the road was resurfaced, but this isn't a legal prohibition. 

There is some usage in OSM of motor_vehicle=discouraged and I could see an argument for this, but at present anyone seeing an OSM-based map would expect this to be a traffic-free road, and it certainly isn't.