I've noticed strange thing - when I put "Start a Task Process" in a loop (n-times), participants got n-emails with Task Assigned notification and n-1 emails with Task Canceled notification.
Settings for "Start a task process" are:
-"Assignment Behavior" set to "parallel (all at once)"
-"Assign a task to each member within groups" checked
-"Wait for task completion" unchecked
Example: I've got loop with 2 iterations (razy, dwazy) and I received 3 email - 2 with task notification (for "razy" and "dwazy" task) and 1 with task canceletion (for "razy" task).
Obviously task "razy" is canceled/deleted (no item on Workflow tasks list).