As everybody has pointed out, the behaviour in real-life is that any events already stored in the event registration refnum will still be there. Any attempts to send further events will fail, however, since the event required for this is now destroyed. I do this reguslarly, create event, register for event, send event, destroy event, eventually handle event. Works fine.
For me, the documentation needs to be amended to clarify this issue.
"no longer receive the event" is ambiguous. Events queued up until the point of destruction will still be handled, and events attempted beyond the point of destruction will not have any effect.