UPDATE – This is actually by design. As the inside of your design may have triangles with large angles that may need to be maintained. Still I would prefer this as an option here to look everywhere or outside only..
Surface Properties -> Definition – > Build -> Use Maximum Angle
This feature should give you the ability to weed any triangles in your surface that have an angle greater than the specified angle.
Obviously for corridor models this is quite useful as they are built by almost parallel sections triangulating between one another. So anything outside this wonderful playground should stand out, like below.
For some reason though, when I apply a Maximum angle of 95deg it does not weed all the triangles. It leaves lots of them with angles greater than 95 deg. See below
