I think they must be?
Some are showing the wrong direction, eg Church Road and Lower Church Street in Chepstow. These are 18954933 and 18954931 in OSM. The OSM map shows the arrows in the correct direction and C.T uses the roads in the correct direction. It's just the chevrons that are drawn the wrong way round.
At a guess it is because for those roads the OneWay tag is -1, other nearby one way roads that get marked correctly have OneWay=yes. It seems oneway=yes is used when the road was drawn in the direction of traffic flow and -1 is used when the node list of the way is opposite to traffic flow. Seems the routing understands both OneWay tag variants but the chevrons are drawn according to the direction of the node list.