I read this article more as a complaint about what Apple communicates about what they will do on maintenance than as one about what they do in maintenance of their software.
For Apple, there’s https://support.apple.com/en-us/HT201624, but it only lists how long hardware is supported (that list does go back a long time, though. It’s good to have official confirmation that the Macintosh 128K is obsolete)
“As far as macOS goes, everyone will tell you that Apple supports the current version for about a year before it’s replaced by a new major release, then provides two years of security updates for it. The strange thing about that is Apple doesn’t seem to have committed that to writing, and I’ve searched long and hard for its official policy on many occasions”
With some other companies (typically more business oriented), you can know the moment you buy their software how long it will be supported. See for example https://docs.microsoft.com/en-us/lifecycle/faq/windows.
For Apple, there’s https://support.apple.com/en-us/HT201624, but it only lists how long hardware is supported (that list does go back a long time, though. It’s good to have official confirmation that the Macintosh 128K is obsolete)
For Mac OS, the best you get are educated guesses from third parties. For example, https://eclecticlight.co/2021/09/22/how-long-does-apple-supp... says
“As far as macOS goes, everyone will tell you that Apple supports the current version for about a year before it’s replaced by a new major release, then provides two years of security updates for it. The strange thing about that is Apple doesn’t seem to have committed that to writing, and I’ve searched long and hard for its official policy on many occasions”