Even if that's the intended meaning of literally, it is still a reckless exaggeration. I'm pretty sure that Stephenson's endings are no more abrupt than some of Shakespeare's (check out Hamlet and Macbeth) or some of Frank Herbert's (see Dune and Children of Dune), and I never hear anyone go out of their way to describe either of them as being unable to write endings.
Everything from Stephenson after Anathem is an unremitting slog. He needs an editor who won't back down from telling him he needs to cut a third of his pages.
No, no it doesn't. Are you talking about the recent movies that split the first novel into two movies? The novel Dune ends after Paul defeats his enemies and becomes emperor.
I know that, I've read them too. In the SP, and in this thread we're discussing endings to novels. No one is complaining about a series that isn't finished due to the author's death.