I think you can bring contamination claim to every public benchmark results nowdays: models are trained on TBs of data crawled from internet, and there is no guarantee benchmark is not leaked in some way.
If we're comparing benchmark deltas between different fine-tuned variants that share the same base models, that seems like the bare minimum we should expect to come along with performance claims.
Even I am to grant that their subscription product has some secret sauce they want to keep close to the chest (ignoring for a moment their paid product is GPT-4 based), not doing the same for all the models they release to the open source community free of charge with a commercially-permissible license seems suspect.
I realize this sort of open source contribution is mostly for marketing purposes, but being critical of the performance claims I think is still valid nonetheless.