Oh it’s simpler than that. They just go around the requirement via loopholes in the agreements. They know they’re required to give priority, so they just make the freight trains too long to fit on the side track on those routes. So if there’s a conflict, the freight train physically cannot get out of the way and the passenger one has to.
Must have been one of these.
https://youtu.be/mg79n_ndR68?si=RyDEQnOrlEexiccS