Why are they trying to discover these things? Why are they exploring physical geography or a town's social network? These aren't goals in and of themselves. These are means to an end. The point of exploring physical geography, for example, is to find stuff that's interesting to do. The player's don't care about the town's social network in and of itself. They are discovering these things so they can then go do something they actually want to do.
IOW, limited knowledge is simply a means of stalling the players from doing whatever it is they actually want to do while they spend time uncovering information that leads them to the stuff that's of actual interest. The players don't really care if the Dungeon of Nasty Badness is in Hex 1211 or Hex 1213. They want to go to the Dungeon of Nasty Badness.
This is conflating means and goals AFAIC. If this is the "ideal" of sandbox campaigns, then, well, to me, that means that much of the time in the "ideal" of the campaign is spent doing stuff just to get to the stuff that the players actually want to do. I believe the term for this is a "rowboat campaign" where the party just kind of wanders around aimlessly until they have achieved a sufficient amount of DM prepared information and then they actually get to do the stuff they want to do.