Although even in Vivien's link, the sentence before the "strong recommendation" states that it can be done. If MS send that out in their documentation, they have an obligation to stand by it.
That said, I agree that it's one of those upgrade paths that's fraught with unnecessary gotchas, so I doubt many people would follow it. When all's said and done, an evaluation is a form of test, so I can't personally think of any time when I'd let an evaluation edition of any software near any instance of mine that couldn't be blown away with impunity.
Semper in excretia, sumus solum profundum variat