A clean partition is not required, update 3 only requires Update 2 to already have been installed.
Well, what was the latest version released as a complete ISO then? OS4.1.2? OS4.1.1? To make a clean-slate install you would have to start from there (wherever that is), and then start adding all subsequent updates, one after another, until you have reached the latest one...
The situation is no different on MorphOS
...which is very different from the MorphOS way. You can download any of the above MorphOS versions and boot/install directly from the CD. Clean-slate, or upgrade, your choice. But here is the thing - you don't have to! The reason to why only the latest version is linked to from the MorphOS Team's webpage, is because that's all you'll need! No need to install x amounts of prior OS versions, and then upgrade from that.
Only one download needed, always, and it's an ISO, always!

MorphOS hides the real MorphOS system files in a way that is not done on OS4.
Yes, and this didn't happen by a random coincidence, it was a design decision. And a very good and clever decision too, with hindsight to this OS4.1.3 release (and others as well)! Upgrades goes much smoother on MorphOS, thanks to this!
But there have been many cases where users have replaced Morphos classes or system files then run into problems.
If some moron breaks all recommendations and instructions and starts removing or modifying things in the system's exclusive, "don't-touch" MOSSYS, and starts relying on that, rather than use the proper user-space SYS for this, then they are completely on their own when it's time to update, and they have only themselves to blame for any problems. The "moron-protection" only goes that far you know... :p
That is no different than OS4.
All this is obviously *very* different from OS4...
