Don't over-think this.
Nearly every porch light I've seen has actually been placed in a 'damp' location, rather than a wet one.
Another thing to consider is that a cover isn't needed for a receptacle to pass a 'rain' or NEMA-3R test. All one need do is slightly recess it, or to point it downward, and the opening will not collect the 'rain'- water droplets that are falling at approximately fifteen degrees from the vertical.
As far as dates go, it wasn't until well into the 90's that UL paid any heed whatever to "NEMA" enclosure specifications. UL didn't even want to admit NEMA existed. Instead, UL had their own criteria for 'dry,' 'damp,' and 'wet.'
