I don't think aggregating the whole platform into one number is fair. It's like adding the whole aws into one number
Instead it's nice to think about how you can express the state of a complete system as a single number. It might be you divide active user sessions by database-connections, and then scale by memory capacity.
But as a single digit you can then get used to normal ranges, and have it always visible somewhere obvious. A single number won't show details, but when it changes you can go look at the specific metrics. It's a cute shorthand, and it can work well as a basic "are we normal" check.
there is a subset of the site that pretty much everyone uses — git, issues, pull requests, actions — and if any part of that is broken then the site is broken and the status page should indicate how often this happens
This is a pretty ungenerous take. You could look at it the other way: if I don't use actions then it's useful for me to know that only actions are broken, and I can continue in my normal usage. If you bundle everything up then the status page is reporting an unhelpful false positive for me.
example (not sponsored, i barely use codex and today's the first time i've ever had to look at this page; i don't know how much they're fudging the individual numbers or not reporting minor incidents):
most people who use chatgpt don't use all of the components under the "ChatGPT" heading. for codex, i don't use the vscode extension or codex web. etc
No one cares that much if repo wikis, commit stats or gist had these issues. It's the combination of inter-dependent services that are used in combination, like PRs, actions, discussions, etc.
If one were to build a single percentage for each of these components of both systems, github would still lose. Maybe it's a few days without outages more but this isn't a comparison.
They would love if everyone on the platform used all of the features and had massive lock-in right? So if some part of that is always broken, it’s not a confidence booster for users to adopt more of the feature set.
Sure the more things you use the more likely it is that one has an issue but clearly stability isn’t a goal for these type of companies anymore.