Hi,
By looking at the EV19, I noticed the following:
- At zoom level 8 (https://cycle.travel/map?lat=48.8231&lon=6.8665&zoom=8) it looks like the veloroute stops at some point.
- At zoom level 11 (https://cycle.travel/map?lat=49.5791&lon=5.1169&zoom=11) we can see that indeed, it changes from National to Regional a bit south east of Sedan.
- When looking at the OSM objects, it seems that it comes from the fact that the superroute "EuroVelo 19 - The Meuse Bicycle Route" (OSM relation 7298586) includes a regional one ("Voie verte Trans-Ardennes", OSM relation 370404) starting from this point (rather than road segments).