cannot unregister EVENT_RAID_SCORE_NOTIFICATION_*

[sirinsidiator]

I am currently playing around with the notification system and have encountered some strangeness that I cannot explain to myself.
My test setup:

ZO_PreHook(CHAT_SYSTEM, "OnNumNotificationsChanged", function(self, totalNumNotifications)
    d("changed from " .. tostring(self.currentNumNotifications) .. " to " .. totalNumNotifications)
    if(totalNumNotifications > 0) then error("test") end
end)
 
zo_callLater(function()
    d(NOTIFICATIONS.eventNamespace)
    d(EVENT_MANAGER:UnregisterForEvent(NOTIFICATIONS.eventNamespace, EVENT_RAID_SCORE_NOTIFICATION_ADDED))
    d(EVENT_MANAGER:UnregisterForEvent(NOTIFICATIONS.eventNamespace, EVENT_RAID_SCORE_NOTIFICATION_REMOVED))
 
    EVENT_MANAGER:RegisterForEvent("test", EVENT_RAID_SCORE_NOTIFICATION_ADDED, function() d("add event") end)
    EVENT_MANAGER:RegisterForEvent("test", EVENT_RAID_SCORE_NOTIFICATION_REMOVED, function() d("remove event") end)
end, 1000)

I expect this to hide the raid notifications until some other event refreshes the notification manager.
When I load the addon I get:

KeyboardNotifications
true
true

Which means it has unregistered both events successfully, but instead of ignoring the raid notifications it still handles them as if I never unregistered the event.
When I already have got some of them in my notifications panel and press the delete button, it shows

remove event
changed from 4 to 3

and then throws my error with the following stack traceback:

	[C]: in function 'error'
	user:/AddOns/test/test.lua:42: in function 'hookFunction'
	EsoUI/Libraries/Utility/ZO_Hook.lua:19: in function 'OnNumNotificationsChanged'
	EsoUI/Ingame/Contacts/Notifications_Common.lua:705: in function 'ZO_NotificationManager:BuildNotificationList'
	EsoUI/Ingame/Contacts/Notifications_Common.lua:678: in function 'ZO_NotificationManager:RefreshNotificationList'
	EsoUI/Ingame/Contacts/Notifications_Common.lua:58: in function 'ZO_NotificationProvider:PushUpdateToNotificationManager'
	EsoUI/Ingame/Contacts/Notifications_Common.lua:34: in function '(anonymous)'

When I let myself get killed and revive, it also throws the same error two times in a row.

Notifications_Common.lua:34 is inside the handler function that gets registered to both events in question and is - as far as I can see - never used anywhere else.

Maybe somebody can explain to me what is happening.