I'm documenting this just to help out the next person who might find this confusing.
Earlier this week, Synology qualified the Hitachi 3TB HDS723030ALA640 drive.
While shopping for this drive, I found this exact product model number on a couple of websites -- but I found a slightly different product model number on several other websites that offered attractive pricing (including NewEgg).
I called Hitachi for clarification -- and they told me that they only produced two - 3TB drives -- a desktop Deskstar version -- and an enterprise Ultrastar version.
Digging deeper, I found out that the alternate model number, which is H3IK30003272SW (0S03208) -- is exactly the same as the Synology-qualified drive -- but it is the "Internal Drive Kit" bundle -- which apparently includes mounting screws and a SATA cable.
So -- long story short -- I believe the H3IK30003272SW product advertised on a number of websites -- is identical to the HDS723030ALA640 drive qualified by Synology.
I have just ordered the NewEgg drive and will provide further comment -- if I find any actual differences.
Hope that helps.