I highly doubt professional or even amateur quizzers wouldn't use flashcards. Especially armed with a SRS algo, it would be the most efficient way to learn to quickly recall the type of info needed for quiz bowls
Roger Craig famously used Anki and was one of the top jeopardy players for a while, and I believe he got some push back from the likes of Jennings and others who thought flash cards were cheap and the only right way to do trivia is "naturally", by just reading a bunch of random shit all the time.