@anon37303405, I’m afraid your workaround doesn’t permanently delete the tasks, it just deletes them. I tested and those were the results I got. Maybe you should double check using Advanced Search > Add Filter > More > Deleted > then click the Deleted box now added to the form (I have no idea why Asana still doesn’t set that one by default after you pick “Deleted” from the more Menu).
Unless I’m mistaken, you should update the title of this thread.
Thanks,
Larry