The third-party aspect is irrelevant, but while high downtime on any product looks bad for the company and the division, I consider GitHub Copilot an entirely separate product from GitHub, and GitHub Copilot downtime doesn't interfere with my use of GitHub repos or vice versa, so I'd consider its downtime separately.

GitHub Actions, on the other hand, is frequently used in the same workflows as the base GitHub product, so it's worth considering both separately and together, much like various Azure services, whereas I see no reason at all to consider an aggregate "Microsoft" downtime metric that includes GitHub, Azure, Office 365, Xbox Live, etc.

The most useful, metric, actually, is "downtimes for the various collections of GitHub services I regularly use together", but that would obviously require effort to collect the data myself.

My use of GitHub is like yours; I depend on Actions, but I couldn't give less of a damn about Copilot. However, Microsoft has tried to get people to adopt Copilot-heavy workflows, where Copilot plays an integral part in the pull request review process. If your process is as Microsoft pushes for -- wait for Copilot to comment, then review and resolve the stuff Copilot points out -- then Copilot being down means you can't really handle pull request, at least not in accordance with your standard process. For people who embrace Copilot in the way Microsoft wants them to, a GitHub Copilot outage has a serious impact on their GitHub experience.