I have no idea whether this applies to Lex, or if there are better explanations, but... he probably just asks. In my limited experience with my little podcast in the sports analytics world, I'm consistently surprised by who says yes, and how few people say no. ~90% of the people I've asked to be a guest have said yes, and those who have said no haven't done so because they're "too famous" or something like that.
Not OP, but they're referring to situations when players call their own lines. (Virtually all amateur matches.) If you are horrible (or blatantly biased) at calling lines, your opponent can call the tournament referee, and you may end up with a line judge. But that takes time, and only happens after you aggravate your opponent. If you wait until a key moment to make a bad call in your favor, your opponent won't be able to reverse it, even if they call the referee and get a third party to call the lines for the rest of the match.
This is a particularly big issue in competitive junior tennis, unfortunately.
Those Antarctic islands are the Balleny Islands. I took a cruise a couple of years ago from NZ to Antarctica, and we were able to land on Borradaile island [1], one of the Ballenys. I can't find my notes for the exact figure, but the historian on board said that, including us, only a few hundred people had ever set foot there. Many expeditions pass within sight of them, but landing is treacherous--IIRC, we went onshore for about an hour in the morning, and by lunch it no longer would've been possible to do so.
Per the article, he spent years in concentration camps, but only a few days at Auschwitz.