I assume that this is the scenario you are describing. Put me right if I have got it wrong.
While Defragging your HDD the schematics show sectors that are "Unmovable".
Your question is!
"How can these sectors be copied to another drive if they are unmovable?"
I do not know for certain, but have always assumed that the Schematic is just that and bares little relation to the actual HDD. In this case the word "Unmovable" means that on that HDD the information is limited to a single sector.
However when I think of it that analysis is full of holes. Maybe someone really knows.