That is a OFPW flag Planck is referring to, and is currently not supported by wrptool.
If your test units are not sticking to the road, first try setting their status to safe/careless and formation column. That tracks on valid roads much better.
If you are using narrow country lanes with hedges that trigger the AI collision detection engine, or are using new road objects that are not yet completed - recognized, you can try the manual AI paths found in the 3WX misc pack to try to 'force' the AI down the road.