Anthropic removed raw CoT from all models since Sonnet 3.7 (released February 2025), all Opus 4.X models have censored CoT, yet Chinese labs continue to distill from them, proving this restriction wasn't an insurmountable hurdle.

There are some outputs that are highly valuable and cannot be censored, such as tool API calls or agentic tool usage, which is precisely what Moonshot was accused of harvesting/distilling.

Tool call harvesting was enough of an issue that Anthropic began inserting spurious tool calls when they detected distillation attempts, trying to poison the distilled data.

There is certainly more data the labs are training off of, but that's difficult to know without insider information.