LLMs are limited both by what they’ve already seen (training set), and the inference (prompts/input).
I suspect the question you want to ask is: Is the expert (“human in the loop” as @bitsondatadev puts it) responsible for reviewing LLM’s output putting in the requisite work to evaluate it for correctness and completeness?
SoTA LLMs from frontier labs are really, really good at code. I wouldn’t be surprised if they are decent at code-focused cryptography audits, too. I can tell from experience that LLMs in the hands of an expert will produce vastly different & potentially highly useful results than a “script kiddie” might. In short, it all depends on just who is wielding the sword prompt.
All that said, rage-bait marketing (ex) is also a thing these days…