Can confirm.I'm running dupe finder on (3) drives. All searches involving any directory but the main return nothing and are instant. I started with nothing but (3) subdirectories and the search returned nothing. I ran (3) searches after that. Each one was for a whole drive and (1) subdirectory on each of the remaining ones. Each time it returned dupes on only the top directory level search.
If anybody needs a workaround, you can still search a whole drive and make a list of exclusions.
Windows 10 fully updated
I'm admin on this machine.