I believe you can sort folders in Grid View, but only in sub-folders. What I mean is if you have a TOP folder and an A B and C sub folders, if you're looking at all of the images in the TOP folder you can't sort them but if you're in the A, B or C subfolders, you can sort the images within those folders. Think of it as if you were in Windows Explorer, or Mac's Finder. Looking at a folder shows you the icons of the folders contained within that folder, but you can't do anything with the files contained within those subfolders. To do anything with a specific file, you have to navigate to the folder containing the file.
HTH
Mike.