I just tried Preview and the window that opens when I hit View Details (see below) is the exact same window as you get in Image Capture. So, my take is that although Preview is open, it is using Image Capture's capabilities just as I can open an app called "Epson XP-810 Series" which will give me the exact same window and is, in fact, using Image Capture. Regardless of that fact, the fact that the OP can choose to use the Flatbed instead of the Document feeder in that window is still the point I was trying to make: the choice is available, albeit one window later than the OP wishes it to be. At least that is how I understand this entire dialog.
