Thanks @pdeleuw for the reminder, I will bring this to the documentation team to update/improve the explanation around this since it's relatively new, and I agree it should be clarified better in the documentation. Firmware upgrade email alerts/reminders go out to your Network-wide admins, not Org admins, so they will be configured on the Network-Wide > Alerts page and admins defined on the Network-Wide > Administration page.
The Special Announcements under Organization > Settings > Administration is meant to be Organization-wide and not specific to any individual network, and would include things like what you might find under the "Announcements" menu in the upper right next to the Help menu, and can include security advisories, feature deprecation notices, hardware advisories, and license notifications. There is also checkbox to disable that last one on license notifications.
Only full Org admins with full read/write access will receive those special announcements (with or without the license info alerts based on that checkbox) and you can either select it being sent to all Org admins as defined on the Organization > Administrators page, or you can feed these special announcements into an email alias of your choosing by selecting the mailing list option.
You are correct that "All network admins" does not necessarily include the Org admins. But full Org admins are also network admins since they have full read/write access over all networks in that Org. When you configure alerts to be sent to "All network admins" this by default does NOT include the Org admins, although for individual network alerts you can add Org-level admins using the custom recipients box. When you go to the Network Wide > Administration page, you can also view the Org-level admins there but not edit them (go to the Org > Administrators page) and you can also add/edit your network-wide admins.
I'll make sure the documentation team is reminded to update the notes regarding the special announcements section.
