They have a catch-all that a route shown open may in fact be closed or vice versa when on the ground reality does not agree with a map. There is a lot of that I've seen lately. Perfectly intact, existing Carsonite with route numbers that have not been recently mapped and inventoried.The TMPs that I've been involved in and aware of close all routes that aren't designated as "open" so while the old trails do decay, and would create some decent tracks, it would be illegal to take them. Is that not the same everywhere?
An example of this verbiage from an Emery County OHV Travel Map, "Unless designated as being open for public travel for OHVs, either by the "Off-Highway Vehicle Travel Map", or by signage on the ground, all Emery County Roads remain closed to travel for OHVs."
Some do show up on historical maps or in disorganized attempts by BLM or USFS to fulfill Congressional requests when legislation is introduced, but resources are limited so much of it remains incomplete and political polarity makes rational discussion seemingly impossible. These are routes that one side says are already closed (since they do not exist on stalled 10-year old BLM map updates but have been signed for decades), which by the language seems to me to be disputable and a potential compromise position.
Highlighting this to keep a route open means I'm a monster who want to encourage side-by-sides without mufflers traveling at full speed off route through riparian ecosystems killing endangered species. When the fact is I do not want that and think some routes should be kept non motorized or non mechanized. It's not appropriate to drive or ride a bike or perhaps enjoy even the advantage of machines at all (like the sound of a clanking alpine touring binding) everywhere. But there are many areas where an occasional truck or bicycle aren't going to upset the Wilderness-ness much and it could be a conservation area or monument or something where open travel is restricted but not by default eliminated.