Ultimately, it doesn’t bother me that Microsoft has chosen to include Windows Server 2008 R2 content on Windows Server 2008 exams. Windows Server 2008 R2 was a minor release that built on Windows Server 2008, so including questions about it on the Windows Server 2008 exams seems fair.
What does bother me, however, is the way in which Microsoft has quietly implemented the changes. In doing so, Microsoft has set a precedent that exam objectives can be changed at any time without notice. If Microsoft continues to follow this new precedent, then those who use traditional study guides for exam preparation are going to be in trouble, because the guides may more quickly become outdated.
As such, I predict that publishers who have traditionally published study guides may start producing online content instead, and that this content will evolve with the exam objectives. An entirely new cottage industry may form around alerting exam candidates that exam objectives have changed.