This post on Reddit about an HOV route in Belgium/France is interesting. Could this be a bug or is there HOV lanes mapped along this route somewhere?
There is an HOV lane near the border with Luxembourg. It is mapped correctly and at certain times of the day, being allowed to use that lane can shave off quite a bit of travel time: https://maps.app.goo.gl/qArKBUzwYmwXwP6U6. But we don’t use that symbol over here, so I can understand the confusion.