Under-developed compared to what? It’s inhabited, it’s got a castle at Flint’s Finger, etc. If I had to guess, I’d say that Cape Kraken probably doesn’t have very good soil, since the presence of the Flint Cliffs and the name of House Flint suggests that there earth is rocky and rather poor in topsoil.
And the wetwood seems to be part of the Neck proper, from context, as opposed to part of the Cape.