Care to cite those cases, due to the only time you would be able to have NM outside, is at a junction box to attach a light, coming into an attached junction box on the outside of the structure, that the NM enters in from inside the structure.
Even under porches, the only time you can run NM, is inside the "attic" space of the porch roof. Otherwise if it is exposed underneath with no sheathing, it is UF or conduit with THHN/THWN inside, to the junction box. You can transition from NM to the UF or THHN/THWN at the junction box at the wall, and that is only how far it can go when out in the elements.
Now if the space is an "All Season Porch", it is again dependent on your area, what they allow for use in that area, and how they classify the space for use in electrical wiring practices.
My area, you cannot use NM in an All Season porch even. It has to be conduit or UF, because it is considered an area that is not a part of the inner area of the structure.
Again, rules vary area from area, and each area can enforce them as heavy or lightly as they want.