I think what they're saying is that X can be and independant OS. Many people are running just 10.1 w/o any classic. I, for instance, don't have 9.x installed on either of my computers.
You only need Classic if you need to use programs that only run in 9, which is probably 85% of the Mac software. I think Apple didn't incooperate a 'Classic' within X because they want software companies to carbonize their software. If a Classic was in X, they wouldn't have to do that and the transition over to OSX would theoretically take a lot longer.