I think this is a really important point that is getting overlooked in most conversations about GitHub's reliability lately.
GitHub was not designed or architected for a world where millions of AI coding agents can trivially generate huge volumes of commits and PRs. This alone is such a huge spike and change in user behavior that it wouldn't be unreasonable to expect even a very well-architected site to struggle with reliability. For GitHub, N 9s of availability pre-AI simply does not mean the same thing as N 9s of availability post-AI. Those are two completely different levels of difficulty, even when N is the same.