New versions of OS X and macOS have been released as full versions, but in OS X (ie 10.##) the App Store and System Preferences methods are absolutely in-place upgrades. Big Sur is actually a full system update via any method.
"For I'm not sure how long, OS installations have been effectively click and..." agree to legal contract titled 'Terms and Conditions' that, if anyone read them, would clarify a TON of technical misconceptions and speculations (but ironically does not provide much legal clarity).
I've recently installed OS X 10.10 - macOS 11.0 dozens of times each with no eyes or hands, and at least one of the people involved was frustrated every single time. People shouldn't have to have experience installing every release of the last fifteen years to install the latest without struggling.
"For I'm not sure how long, OS installations have been effectively click and..." agree to legal contract titled 'Terms and Conditions' that, if anyone read them, would clarify a TON of technical misconceptions and speculations (but ironically does not provide much legal clarity).
I've recently installed OS X 10.10 - macOS 11.0 dozens of times each with no eyes or hands, and at least one of the people involved was frustrated every single time. People shouldn't have to have experience installing every release of the last fifteen years to install the latest without struggling.