I interpreted your original comment, "Uptime has never really been Heroku's strong suit", to refer to
application uptime. I guess you're actually referring to something different.
AFAIK, when any other provider speaks about "uptime", they're referring to whether or not the service they're selling is up and running. For AWS, that'd be whether your instance or ELB is up and running as expected. For Heroku, it's whether your app is up and running.
Issues in the control plane that affect your ability to make changes to your resources are generally outside the scope of any "service uptime" numbers you see published (unless that uptime is specific to the API/control plane).
Edit: We do our best to publish info for both the service, and for its control plane. I would agree that our status site categories ("production" vs. "development") might not be the best way to label this split. Previously we used "app operations" and "tools". We may yet change it again.