I may be interpreting it wrong but Goenka says that vipassana is the ninth jhana, not that the ninth jhana is vipassana. I think the only intended meaning of this is that vipassana is more important than all the jhanas. But I'm not sure, as I've heard this a long time ago.
And the Blessed One addressed the bhikkhus, saying: "Behold now, bhikkhus, I exhort you: All compounded things are subject to vanish. Strive with earnestness!"