So I dug a little deeper into the issue and found where/how, in the Iced code base, events are being “produced”. Based on iced/winit/src/conversion.rs, my understanding is that Iced events are simply a “remapping” of winit events. That being said, I now realize that my question has more to do with winit itself than with Iced.
So I ran a Google search for rust winit how to get cursor events while hovering file, and my first hit was Drag&Drop API / HoveredFile, DroppedFile, which corresponds to a GitHub issue (in the rust-windowing/winit repo) where the user exactly describes what I am observing.