I am also very concerned about this. The fact that also if the players get to far away from you they disconnect or something I think I heard. I think though the reason behind why you cant build bases in other peoples worlds and such was due to funding as the developers had actually been limited I think Microsoft is testing the water first and if state of decay 2 does well I think the third instalment will be the actual grand scale one.
I dont mind the tethering so much, as we would normally run around together when we coop anyway, but the not being able to help build and use resources etc, thats just very disappointing and makes it barely co-op at all. But we've finished with Dying Light so this will do for some team zombie killing for now.