Anthropic needs to teach their systems to propose a fix too. Detecting a coding problem and proposing a patch is what we should expect from a company with supposedly the best coding LLM.
Of course it's trivial to have an LLM generate a fix, too. They probably do. It doesn't mean a project (1) wants to take an LLM-generated fix at all, or (2) can immediately commit an LLM-generated fix without review (which takes time).
The reason Anthropic isn't proactively sending patches is, I suspect, that those patches would not be welcomed, because trust in the models isn't currently at the point where maintainers are willing to merge them without human review, which takes approximately as much effort as writing the patches themselves. You can imagine the wailing and gnashing of teeth about "slop PRs" and "extractive contributions" that'd be all over HN.
If they actually were sitting on a PR gold mine of vulnerabilities they wouldn't be throttled on review resources while artificially inflating/misreporting their numbers. They would be diverting resources to clear the review queue.
It's fake and it always was fake.