Scheduled action no interrupt

At the end of the run, ScheduledAction unsubscribes itself which triggers a set of cleanup actions, and since it is also the way to cancel a running action, it calls future.cancel(true) as well which interrupts the task in the underlying executor framework. However, on a normal completion path, it is unnecessary to interrupt itself at the end of the run since it will complete anyway, and not to mention, it has some performance implications for short running tasks. The downside is the +4 bytes per ScheduledAction.
I don't understand. the ONCE_UPDATER would be sure we only call `unsubscribe` once, and it needs to be called at least once, so what performance benefit happened by removing ONCE_UPDATER that now allows it to possibly be called more than once?