Look at the graphical picture of the absin again. you'll see that the Skarch is actually still surrounded in by the mountains; yes, it's partly closed off, but it's still closed in from everthign else, except for on it's west edge.

And Gaudigulch is fully in the basin, as it it is on the borderlands of the desert, righta t the base and even sort of part of the razine Mts.

To be outside of the basin, one needs to fully go outside of all the mountain limits.