In this case, the GPS really wasn't an issue, nor was the quality of the maps. Closure data was reported for the main road, which was closed. Most forest service dirt roads don't close for snow in this area, but it is up to the user as to whether it is useable or not as they don't perform snow removal on them for the most part. If they are going to use these roads, what type of vehicle is required to use it is up the user. It may be 4X4, snow cat, snowmobile, atv etc.
As for the quality of maps, surprisingly given the capabilities of technology, maps are still pretty bad in many areas. That said, never seemed to stop me from exploring the western backcountry for decades without incident.