[D] How do we know Closed source released benchmarks aren't being heavily optimized, through outside means?

I've recently started working with ML and NLP, so I'm sorry if this sounds Naive.

Unlike Llama 2 or other open source, we don't have access to the model weights for GPT-4, Claude or Bard, so Benchmark Evals are being run through either APIs or the chat Interface. So how do we know that the model isn't being Boosted by custom web-searching abilities or RAG? While GPT-4 might have a turnoff option, I'm pretty sure Bard is always online, being …

apis bard benchmark benchmarks claude evals gpt gpt-4 llama llama 2 machinelearning nlp open source through