You just read the news too fast. WMO announced that, after evaluation by a committee, they have validated the 18.3°C temperature recorded in February (i.e., in summer) last year:
GENEVA, 1 July 2021 (WMO) - The World Meteorological Organization
(WMO) has recognized a new record high temperature for the Antarctic
continent of 18.3° Celsius on 6 February 2020 ...
Supplemental to Jean-Marie Prival's answer:
The February 2020 event was already discussed here in a question posted the same day this went public: What is the second thermometer in the image from the Esperanza Antarctic temperature record?
The tweet contained an image of a literal analogue ...
To complement the other answers: it is also true that the coastline in that region hasn't been fully documented yet, primarily because a large amount of it is covered by glaciers.
As an example, Sif Island (arguably of moderate size but still) was only discovered last year in the Amundsen Sea embayment (at the left end of your second map) by the THOR ...
The key sentence here is
(not sure where the dataset is from)
Every cartographer has to decide what level of detail to use. Mathematicians discovered the Coastline paradox for themselves in the 1960's, but it has always been a fundamental part of cartography.
Different sources of data will come out of different methods of data collection, digitization, and ...