Look at the copy and paste from the user manual below.
I take that to mean that it isn't enough for the source drive to be WD brand and that in fact the destination drive must be WD brand.
I have used the product successfully to make images, but have not yet done a restore.
All my drives are WD, so I cannot say for sure if it would fail if a restore or clone were attempted to a Seagate, for instance.
Given the wording, I think one would be foolish to assume it will restore to other brands, but I'd certainly like to see someone step in here and say they have successfully done so.