I think an option to delete all associated approval tasks if the flow is canceled or terminated is needed. Maybe this setting would make sense as a paramater for the entire flow or as a paramater within the Assign a Task action.
Currently the tasks appear to be left orphaned and assigned to the user to approve or reject even if the flow has ended and the approval is no longer need. By having this option we can remove the clutter of orphaned approval tasks sitting in user's queues and remove the confusion of the unneeded tasks.