Unfortunately, the term "server-grade" has confused people, including the author of post #1, to expect the "better" grade of server drives that many disk manufacturers produce.
And you continue to confuse them by assuming that there are two classes of drives to which hard disks belong.
As with most things, a little knowledge is just dangerous. A customer would expect a better drive than the ordinary and used in servers. The Time Capsule delivers a better drive than the ordinary (the Deskstar is better than both the Samsung F1 and the WD Caviar GP terabyte drives; it is arguably better than or equal to the Barracuda 1TB [better error rate, rumored but unconfirmed better MTBF, same start/stop], and it is somewhere below the ES and Ultrastar). A customer thinking 'server' means 'enterprise' is just confused in general.
Most sites cut direct to enterprise-products in their navigation links, because that's where the big money is. However, nearly all product pages produce at least three classifications (even Seagate, the only company to use "server and enterprise" and not just "enterprise", splits its 3.5" hard drives into three groups on the main products page).
You know what they say about assuming things. Anyone smart enough to find enterprise drives is smart enough to know that there are more than two broad classes of hard drives, and that the intended applications vary by manufacturer.
The point is not that the Deskstar doesn't meet Apple's criteria for "server-grade", it's that people are being misled because Apple does not explain what its criteria are.
The point isn't that the Barracuda doesn't meet Seagate's criteria for "server-grade", it's that people are being misled because Seagate does not explain what its criteria are.
It cuts both ways. If there's no clear definition, people would be whining because they "expected" a Cheetah when they had no reason to do so. There's no set term by any manufacturer, and the blustery "hold Apple to unusually high marketing standard for no apparent reason" is just a lot of hot air.