the article says the lunar pole region is one of the most frigid places known in the entire solar system, and not much warmer than absolute zero, how could that be ?
No volcanic activity and no atmosphere.
This NASA site says the surface of Triton ( a moon of Neptune ) is 38K, and this is colder than Pluto because of its low albedo. It doesn't have sheltered poles the way the moon does because of the extreme tilt of its orbit. However, one of its poles would point away from the sun for about 80 years at a time, and since its rotation is synchronous with its orbit, the poles should be oblique to Neptune itself, and I myself don't see why the "spaceward" pole wouldn't get colder than the average surface.
The wikipedia article on Triton has a lot of interesting related facts, but I don't see the question of temperature variation on the surface directly addressed. It says, "Little is known about the north pole because it was on the night side during the Voyager 2 encounter." ... and still is, I guess, although it has been 20 years.
I guess the key word is "known," because no temperature colder than 37K has been measured there.
On an astronomical scale, it is much warmer than absolute zero (~40 Kelvin or so). The craters at the lunar poles never see sunlight, so they have no direct heat source. They radiate their intrinsic heat to deep space, which is about 4 Kelvin. There is a small amount of conductive heating through the lunar soil, but it is only enough to maintain the 40 Kelvin or so temperature.