Where in the documentation are you talking about?
For ex. pag 131 of Admin manual of 7.6
I'd bet that the docs weren't updated w/ 2008, unless there is something that says 2008 is specifically not supported using the 'ADK' method.
if you have the ktpass and setspn tools for 2008 you could try it and see if it works... and then get the docs updated.
This is what I am going to try next week.
I'll keep you informed :)