Is it realistic to expect App Store review approval when requesting Full Disk Access? Under what conditions or use cases is such permission typically accepted by Apple?
You haven't really said how you intend to implement what you call 'Full Disk Access.' I currently have two desktop applications with the 'Full Disk Access' capability with read/write permissions. If that's what you are talking about, your application is allowed to have read and write permissions, as opposed to just 'read' if the application is designed to save files to the disk. So, again,
Is it realistic to expect App Store review approval when requesting Full Disk Access? Under what conditions or use cases is such permission typically accepted by Apple?
I would say 'Yes.' But reviewers are not predictable. I had one desktop application rejected by a reviewer 6 or 7 years ago. His or her reason was, as I recall, the application did not write files to the disk when in fact the application did use NSSavePanel to let the user save files to the disk. I had the rejection reversed soon, but you know... That's how the review process works.
Actually, I may be wrong in my earlier statement. I am not certain how one of my desktop applications has gained the Full Disk Access' status although it has read/write permissions. I have a lot of home-brewed desktop applications with read/write permissions, but they aren't listed in Full Disk Access.