My understanding is that the track is closed primarily because of cultural site sensitivity. There is more than one cultural site in this area. A look at the topography shows why it would have been prime real estate : a sheltered rocky hillside just above a swampy, narrow valley with a major river flowing through it.
Don't be under any illusion that taking a 4WD detour that avoids the gate somehow avoids the "Road Closed" status. This sort of sophistry really irks the people trying to manage the place.