All LLM benchmarks have an expiration date once they're released to the public. They get spread so far and wide across the internet and GitHub that you have to assume they're in the training data for every LLM with a cutoff date after their release.

The real question is whether or not the training was directed to optimize for those benchmarks.

The technique doesn't guarantee that the reasoning is returned verbatim because it relies on the weaker model transcribing it accurately. Looking at the charts, there are a lot of dots that aren't in the 1:1 line that suggests that the output is exactly what was provided.