Think of these interviews as a means by which interviewers assure themselves they're working on deeply intellectual CS problems and working with people who are

Think of these interviews as a means by which interviewers assure themselves they're working on deeply intellectual CS problems and working with people who are incredibly intellectually gifted mathematicians practing computer science (like themselves), or that they're of the same caliber as what they believe of developers at FAANG, and it begins to make more sense.