You are allowed to train on the train set. That's the entire point of the test.
>We even have proof that it isn't AGI, since it scores horribly on ARC-AGI 2. It overfitted for this test.
Arc 2 does not even exist yet. All we have are "early signs", not that that would be proof of anything. Whether I believe the models are generally intelligent or not doesn't depend on ARC