Outside of random curiosity, what would be the use case for this?
I can't answer for OP. But in my setup I have one screen which is a home theater and another which is for working and net surfing. 99.999% of the time these days, that means duplicate displays, often with one turned off. But my kid is out of the house.
When he was younger and had pals after school who wanted to watch a movie, it was possible for me to be word processing on one end of the extended display in one room while they were watching the movie on the other end of the extended display in the other room. It was a bit of a chore, if they wanted to stop the movie for a bit and run around, I had to transfer the cursor over to "their side" so they could use the mouse on "their side" to stop the movie, then transfer the cursor back so I could do what I wanted to do.
In theory two mouses with two cursors would have simplified the sharing. As a practical matter I think it would be headache. Anyhow to think of applications just think of two screens in two rooms sharing a PC which is in one room. When you are in room A you need a mouse there to maneuver on the screen there and you need another mouse in room B to maneuver on the screen there. This much I have, but it's duplicate screen mode. On extended screen you have the processing power to satisfy two different uses at once, like streaming a video and surfing the net, and the tricky part of it is going back and forth with the mouse. Cursor battles arose on a few occasions during the "extended screen" era that my son and his friends wanted the mouse at the same time I did. Eventually I built a second computer and kicked 'em upstairs.
Anyhow that's about the only scenario I could think of.
Greg N