GPT-5, maybe not. But somebody somewhere is building something that can do that. And if they can't do it _now_ they have a plan that tells them what's missing. TLDR; it's coming, soon.
and lots of people are spending lots of time and money on AI Coding Assitants... which is more or less the knowledge base you need.
If they could use that structural training to answer queries like "Is there any code path where some_dangerous_func() is called without it's return value being checked"...
You can do this today by querying the AST output by a compiler. Regardless, the parent comment was talking about exploits, not vulnerabilities/bugs. Vulns are a dime-a-dozen compared to even PoC exploits let alone shippable exploits.
You're either being sarcastic or wildly underestimating how hard it is to write an exploit. I haven't written about exploit dev publicly for a _long_ time, but I invite you to read https://fail0verflow.com/blog/2014/hubcap-chromecast-root-pt... for what I consider to be a pretty trivial exploit of a very "squishy" (industry term) target.
XNU isn't the hardest target to pop but it is far from the easiest.
There's nobody more confident in the world, than HN poster wiring about a topic they have no experience with.
There is a huge gap (in the binary exploitation world) between identifying a problematic code pattern and having a workable bug (a reproduction), and even larger one between a reproducible crash and a working exploit (because we're not in the 90s anymore and complier/hardware mitigations are literally always enabled). Current LLMs can cross neither gap, and are not even close to bridging the second one.
