I want to expound on what something that Catastrofe mentioned and 1Louder has described. Now, bare in mind, I am talking in very general terms so this is not 100% across the board. However, I've been doing this professionally since 2004 and have seen how much of this has progressed.
A lot of this overlay data is freely available from different US Federal and state organizations and then incorporated into a basemap on various GPS apps. The data is only as good as how it is collected and updated. I have (well, you as well) access to all the NF MVUM routes, for instance. I'm not entirely sure how often they are updated, but lets just toss out "once per year". So that means if you are viewing data a few months old, some gates may be locked that were not, trails are now closed, or some new ones are open. I'm not in the app side of the business, but from how I work with the same data, I can just about be sure that what is going on is that the data is being pulled per user and added as a layer. Again, this is very similar to how I work, at least part of the time. This is why sometimes you might see a data lag when adding a layer to your basemap.
Boundaries tend to be a lot more stable, such as those for National Parks and National Forests. But the privately owned lands are a different story. When they change hands or get divided or donated, it's up to the local authorities to get that info into the databases, and that would be entirely on them as far as speed of that.
Something else to be aware of is user defined data. If someone goes out and makes a route and the route says "20 miles" it might only be 17 or 18. Some of this is because of how the GPS is collecting data. For instance, I can set my mapping GPS to collect track data in either time intervals or distance from last point. So if it's time and I sit in an area for 5 minutes, it collects a portion of the track every 10 seconds. And in 5 minutes, that is 30 points added to the track and that length gets added the overall track length.
Does not this mean the apps are bad? I don't think so. But what I personally do is use all avenues of available information we all have when I am route planning. A long time ago, while in the military, our route planning was based on paper maps that were often 5-10 years old, if not older. Now, we have Bing maps, google maps, onx, gaia, and a multitude of others. This is like being your own intelligence organization, and it's awesome! And much of this can be viewed though these independent agencies outside of a specific app.
However, I do want to throw huge caution out there, and this is something I very much touch on when teaching classes: maps are models. And just like any model, like a model car, things on the map may nor may not be on the ground and vice versa. Even detailed paper maps like the standard USGS 1:24000 probably wont have creek crossing or super rocky areas. Even comparing historical topoquads from just a decade ago to now, there are tons of trail deletions or additions. Seeing is believing and just because a paper map or gps map says X, does not always mean X in real life. And this is why you need to obey posted signs. I've gone out with a few people who will argue with what the GPS shows vs. what is posted on the ground. I stick with what is posted on the ground. I'm not about to argue with a pissed off land owner because of outdated data.
