The file explorer replacement (FileQuest) doesn't even see the Disk Defragmenter (dfrg.msc) when you look in the system32 folder. C:\WINDOWS\system32\dfrg.msc doesn't even exist according to the file explorer replacement. When you use My Computer or Windows Explorer, dfrg.msc shows in the system32 folder.
Here is a comparison of what each program sees when I view the properties on the system32 folder:
FileQuest - system32 folder
1,734 Files, 122 Folders
Size: 326 MB (342,163,400 bytes)
Size on disk: 329 MB (345,300,992 bytes)
My Computer - system32 folder
6,348 Files, 168 Folders
Size: 1.37 GB (1,472,393,964 bytes)
Size on disk: 1.06 GB (1,139,531,452 bytes)
As you can see, FileQuest doesn't see over 5,000 Files and over 45 Folders. I am positive that F+R is suffering from the same "blindness".
I believe that Windows is changing the shortcut from dfrg.msc (which it can't find) to eventvwr.msc when F+R is used to start the Disk Defragmenter, because it believes that eventvwr.msc is a close enough match.
The strange thing about the problem is that this behavior only applies to external programs referencing these links. If you use the Start Menu directly as I said, Disk Defragmenter starts just fine.
I hope that does a better job of explaining the issue. F+R isn't the only program that is experiencing this problem, i'm afraid.