The list is kind of arbitrary. I don't feel the Amiga UI had any influence on anything what so ever. I was a huge Amiga fan and owned an Amiga 1000 the year it launched and then an Amiga 500 later but other than Amiga's unique multi-resolution system, which really was only something that was a product of the limits of old hardware, there was nothing special about its UX.
There was one difference between Amiga and Mac/Windows that was noticeable on the slow machines of the day: It was more responsive.
Not only did Amiga have preemptive multitasking. The window system ("Intuition") ran behaviour and redraw of apps' widgets in its own task, making them responsive even if the apps owning them were lagging.
Compare that to Windows 3.11 of the day, where the entire GUI would hang while waiting for an app to redraw anything in one of its windows.
I agree - given the Amiga's excellent hardware capabilities for the time, the GUI lacked quite a bit, of course especially compared to the Mac, but even in comparison to GEM.
Similarly where's GEM?
https://en.wikipedia.org/wiki/GEM_(desktop_environment)
I'm sure there's a bunch of others missing for "The History of User Interfaces"