The percent open info given for streams is not reliable. Much of that info is decades old.
And the trend of increased posting of private land just keeps rolling along, as it has ever since I began fishing around 1970, and probably long before that.
Here are two possible approaches for finding these types of streams:
1) Checking Class A and reproduction lists etc., then checking to see if there is access.
2) Starting out with maps of public lands, such as state forests, ANF, SGLs, etc., where you KNOW there is public access, then seeing what streams are on those lands, by poring over the maps.
I mostly use method 2. I don't like worrying about going somewhere, starting to fish, then hitting posted land. Or fishing land that is not posted, and have a landowner come out yelling etc.
There is an enormous mileage of streams on public forested lands.