I think your running into some local idiosyncrasies regarding publishing ethics in Montana. To put this in perspective for much of the states history, crags were word of mouth (with some significant exceptions). This can be because communities are tight knit and there is little reason to publish if you know the only folks who climb in the area (guide books are quite a bit of work), the developer wants to enforce a "pure" experience on other climbers, access is sensitive, or that the developers enjoy having a crag that is uncrowded and off peoples radar. While the latter reasons can be seen as gate keeping, they can also alleviate many access issues that come with increased use. I think its important to keep in mind that our communities are pretty small, even in college towns like Missoula and Bozeman the core group of climbers numbers at most in the low hundreds and most folks know each other and share beta pretty freely. Since the 90's many of the state's areas have found their way into guide books and other print resources, but not all of them and some developers continue to adhere to that no-publish ethic. For example the Humbugs (across the freeway from Maiden) have many routes, but only the Wedge has made it into guides. I haven't made it down to Maiden, but at risk of speaking for the folks who put the time, effort, and money into developing the area, it seems like they want to continue the beta sheet/ word of mouth thing for this crag. In my experience developer interest and tolerance for adding routes to MP varies significantly, but it is probably best to let them take the lead or touch base with them first to see what their position is.
Not sure where you are based out of, but the most productive way to get beta would be to try to connect with folks climbing there. If you can't get that figured out Indian Creek, Hellgate and Avalanche Gulches are near by, have some excellent limestone climbing, are in a few guidebooks, and have much more to offer in the 5.10 range. There is some beta on MP for them, but there are many routes that have not been added. I think this is because most folks who climb there have the book and don't use or need MP rather than the areas being hush-hush. The Big Empty by Ron Brunkhorst may be out of print but is still available at some local gear shops and has quite a bit of the state's limestone documented. An updated guidebook for those and some other central Montana crags should be out sometime in the next year. Stone Tree in Helena has an updated beta sheet for Winter Wall in Hellgate and is also a good place to get beta on other areas if your up this way.
I get that the local/ no-publish thing can be frustrating, but fortunately there are lifetimes worth of routes in the state and many have beta available for them. If your passing through and want to check out some of our rock these are the best option. If you do live here, it may take some time but climb in the local areas long enough and you will connect with some other folks that can show you around to some of the more obscure spots. LCO trail days or other crag TLC events are great for making connections too.