I've got 2 WD20EADS-00S2B0 2TB drives in mine, have had since 1.07 and it's fine.
I think the supported list is just that - what DLink have tested and support. Having 2 of these in my NAS with mirroring makes me feel safe enough that if anything happens to one drive, I have the other. No different to a normal mirror drive solution.....
Hope this is of some help, even if it doesn't answer your question.