Sale might not have been the best word to use, but it's still more or less the idea.
In the Toshiba press release it sounds like Toshiba got most all of the desktop stuff. The server HGST stuff did go to WD though. Or at least the way I'm reading it.
... Under the agreement, Toshiba will acquire the following equipment and intellectual property from Western Digital. 1) Manufacturing equipment for 3.5-inch HDDs for use in desktop PCs and other consumer applications, plus related intellectual property; ...
Either way though, HGST as a brand is under WD and Toshiba is Toshiba.
Or to really go for it,
Toshiba is Toshiba, Fujitsu, and part of HGST
WD is WD, HGST, and Tandon (HGST being made of Hitachi and IBM stuff)
Seagate is Seagate, CDC, Conner, Maxtor, and Samsung's HDD stuff (Conner being CoData & PrarieTek, Maxtor being Miniscribe and Quantum, Quantum being Plus and DEC)
The history of the hard drive market is way too complicated.
Internal HDDs pretty much cost the same per GB, except you don't see 2.5" Internal HDDs come with more than 2 TB. It's strange that those HDDs don't seem to go through the same procedure of being tested as Internal HDDs, I had only 2 portable HDD not work on me (My first one being a 160 GB and my second one being 500 GB), my old 320 GB desktop external HDD works although the casing is damaged.
My other drives 750 GB, 2 TB and my current 4 TB work still, the external case of the 2 TB one is garbage though in build quality. Instead though of using an external HDD to back files up, I should consider a NAS drive someday.