Switching perspectives and switching back doesn't clear the unwanted items in this case.
But I think you're right that this bug may have to do with updating after a script is run. It appears that I'm having difficulty clearing the estimated times from tasks, even with that improved applescript language above.
Here's some more quirky evidence. Tasks in the Inspector sometimes show a Duration of [blank] and sometimes "None." I think I haven't yet hit on the right script language for zapping those estimated minutes fields. I just tried this:
Code:
set estimated minutes of every flattened task to missing value
and now setting the estimated time filter to "Unestimated" shows no tasks and setting it to "1 hour" shows all tasks - quite opposite of what I expected!