https://www.apple.com/os/macos/
https://web.archive.org/web/19991002045556/http://apple.com/...
Pre-OS X (what actually runs in the blog post) it was Mac OS. Then, it was Mac OS X. The first version styled macOS was 10.12 Sierra in 2016.
That’s anachronistic. For example you’d say macOS Tahoe but Mac OS X Leopard and Mac OS 9.1.
https://web.archive.org/web/19991002045556/http://apple.com/...
Pre-OS X (what actually runs in the blog post) it was Mac OS. Then, it was Mac OS X. The first version styled macOS was 10.12 Sierra in 2016.