This tells me Apple plans an iOS desktop mode. You could pair a monitor, keyboard, and mouse with your phone and work at a desk. All your apps, settings, and files stay physically with you, never leaving your device as you carry it to work/school/home/etc. iOS devices would be used like the Nintendo Switch but for desktop computing in addition to gaming.
If it's the latter, I wouldn't be at all surprised to see Apple come up with something that only solves the latter.
And you can get better precision from the Apple Pencil or other styli.
Mouse-support would actually be a step backwards on an iPad; multitouch lets you do things that are impossible with the single pointer of a mouse, such as interacting with multiple UI elements (like sliders, knobs) at the same time with multiple fingers, even across different apps in split-view.
I'm honestly glad iPhones/iPads/Macs don't try to be touchscreen PCs, and I'm glad Apple explores the full breadth of each device's unique strengths, borrowing the best from each other without trying to be each other (except in some cases like wasting the larger screen space on iPads; displaying a single column of Lock Screen widgets or showing 4x4 icons in folders even on the 12.9" iPad.)
External screens as an extension don't really work without some kind of cursor - iOS already supports mirroring the display so this is likely something new.
Of course, the optimistic side of me takes this plus Marzipan and comes to the conclusion that they are putting all the pieces in place for iOS to fully support laptop and desktop form factors and work flows.
Fingers crossed.
But, I don't think we're going to see that...
