In general, the information on maps about dirt roads in the US West can be hard to rely on. Some of the information, as you say, is just out of date.
But it's also the case that dirt roads range from well-maintained and graded to you'd better have a jeep and know how to drive it--and the distinction isn't always obvious on a map (digital or otherwise). Road conditions also vary based on season, weather, and how recently there's been maintenance work done.
Someone stated in an earlier discussion that part of the issue is that a lot of this dirt road data is from US Census TIGER data, which was never intended for automotive navigation. [1]
In some cases, I can tell they used old data. I know one road in particular that did exist 30 years ago, but the forest service deliberately closed off when a rock quarry closed, and it has been re-forested. It still shows on the maps. Another that shows on the maps was planned to be built by the BLM, but never was... yet the map shows it. So I'm not sure exactly what data set they built their maps from, but clearly it did come from data, not actual exploration... because the dirt roads in the American west are just not accurate.