https://www.usap.gov/videoclipsandmaps/spwebcam.cfm

In about a month, the forward motion of the Earth through space will turn the South pole through the planet's circle of illumination for the one and only time in 2018 at Polar sunset.

https://epic.gsfc.nasa.gov/

I assume that although it makes so much sense to treat the planet's two distinct day/night cycles separately via distinct rotational causes, the allegiance to celestial sphere reckoning is so entrenched that people would rather ignore what is correct for nothing more than convenience purposes.