There were probably people who knew that if they went further south they'd not come back. On maps locations like these used to be labeled "Here there be monsters" or something like that.
Probably not. They knew not to go further south because they'd reach the icy ocean of certain death. Because there's no land at 60° South, the winds and currents whip around Antarctica in an uninterrupted circle and there are 100 kph winds and 10+ meter waves most of the time.
See also: "Roaring Forties," "Furious Fifties," and "Screaming Sixties"
I was mocking the attitude that something can't be discovered by one group of people if a different group of people already knew about it.
Columbus discovering the Americas is commonly called a "euro-centric definition of discovery". While conveniently ignoring that literally nobody in Europe knew the Americas existed.
I'm a big fan of Polynesian sailing and would argue that they were every bit the equal of Age of Sail Europeans, if not superior (even despite lacking compass technology). However, their boats and clothing were generally pretty optimized for the tropics, not polar conditions.
I, for one, wouldn't want to be in the Screaming Sixties wearing a cloak and no pants exposed on the deck of a catamaran, no matter how many seal pelts said cloak was made out of. I can only assume any sane wayfinder would say "fuck this shit" and turn North well before hitting the Antarctic shore.