I actually thought we camped there purely because of a convenient rune. Maybe later on the camp site will change as our powers grow eventually going into Mordenkainen's mansion territory?
For likelihood I too prefer to think that they teleport there via (through) a portal. But Larian decides to rain on my parade with the scenes in wich you can see the companions taht you sent back to camp to start walking (maybe I'll add that they just move to the nearest portal).
They have to find a way (just like they did in OSI) to justify the travel [a teleport trinket, or teleport scrolls like in Diablo, and a draw, in the camp, of the runes for the portal].
I like the fact that it is in the middle of wilderness, and the fact that is evolving, but I think Larian could make use of the castle's (or fort) ruins that you can reach walking on the fallen three upon the river, to improve the camp first to a modest village house then to a more city like inn or mansion.
