I'm sure each of the frontier labs have some secret methods, especially in training the models and the engineering of optimizing inference. That said, I don't think them saying they'd keep a big breakthrough secret would be evidence in this case of a "secret sauce" on ARC-AGI-2.

If they had found something fundamentally new, I doubt they would've snuck it into Gemini 3. Probably would cook on it longer and release something truly mindblowing. Or, you know, just take over the world with their new omniscient ASI :)