Matte silver inkjet printables have been for sale here for a while afaik.
edit: ah, I see what you mean now. Not sure if the silver ones here that I saw allow printing including the hub. The white ones do.
At least the ones at xmediatrade seem not to:
although they do seem slightly different around the hub compared to DVDshoponline's and SVP's
DSO silver TY
SVP silver TY
Both claim full surface printable, but not the hub.
Do you have pictures of the discs from that store you link to?