What exactly does the SimPE Clone option "Fix Cloned Files (by wes_h)" do?

I found this thread which deliberately didn't say!

I have discovered that the only way to clone a driveway and have it appear visible rather than invisible is to uncheck this option, but I don't understand why, nor do I know what trouble I may be getting myself into later by not having it checked.

I have not yet used Fix Integrity on the object, but the Group is set to 0xFFFFFFFF already.

Cheers
Mog

P.S. If it helps I will post the package, but I don't know if it is particular relevant here.