You're quite right that LLMs can seemingly do some abstract reasoning problems, but I would not say they aren't in the training data.
Sure, the exact form using the made up word gronk might not be in the training data, but the general form of that reasoning problem definitely exists, quite frequently in fact.
Sure, the exact form using the made up word gronk might not be in the training data, but the general form of that reasoning problem definitely exists, quite frequently in fact.