It is very common for "everybody to be living longer" in trials, even those that fail. Ask md1225 about his beloved Bavi SUNRISE trial.
So that it not "prima facia evidence" evidence that the trial would conclude anything. Even more so as OS is not even the primary endpoint.
And my other points about you theory are also valid.
If the NWBO trial halted enrollment, the final data would be delayed. Even Les stated that they have already penciled in a one month delay due to the hold.
And changing the trial stat plan based on results is still bad form in the eyes of the FDA.