I do think the practice is incongruous in the way it applies "wet" and "dry" at the face of an exterior wall. It is OK to terminate RX in the canopy of an exterior light if the box is recessed in the wall but if you extend this wire through a short sleeve on the exterior wall it is "wet/damp".
I have seen differing opinions about a surface mounted box fed directly through the wall.
It doesn't really matter if this is an insulation issue or a "paper in the jacket" issue, it will still be present in the canopy of that outside light but everyone says the RX is OK there.
I don't understand it but that is the accepted interpretation.
