All the methods and data are not public. We don't know what unpublished methods they're using. You can get most of the pre-training data publicly but they've probably spent a ton of money curating it and are now doing things like buying rare books. The RL training data is all (/mostly) proprietary though, and that's the real secret sauce part.

everybody do be cooking with water. Chinese Labs provided pretty good, primarily cost-reducing techniques, like the sparse attention patterns recently. I'd bet OpenAI and Anthropic use their variants of those too, so they can get greater margin on their tokens - not something they'd really want to / need to self-report.

This is obviously false. There is "secret sauce" because in fact not all the methods and data are public.