TIL Belgium has an Antarctic research station.
https://en.m.wikipedia.org/wiki/Belgian_Antarctic_Expedition
The book "Madhouse at the End of the Earth" by Julian Sancton is a great read for this story of the first humans to spend a sun-less winter in Antarctica.
https://www.asoc.org/advocacy/antarctic-governance/overview-...
Which is to say, most of the people who cared enough to sign the treaty already had existing claims they didn't want repudiated by the treaty (which is why Article IV, in its entirety, also says basically "this doesn't affect any existing claims").