When are the PreCleanupMap and PostCleanupMap hooks called?

So the update a couple days ago added two new hooks called PreCleanupMap and PostCleanupMap, but I can’t for the life of me figure out when the hooks actually get called. game.CleanUpMap() certainly doesn’t do anything. Even just running this test code here…

hook.Add( "PreCleanupMap", "CleanupTest1", function()
	MsgN("We're about to clean up the map!")
end )

hook.Add( "PostCleanupMap", "CleanupTest2", function()
	MsgN("We just cleaned up the map!")
end )

…and then running game.CleanUpMap() doesn’t call either of them. If that’s not what the hooks are for, then what are they supposed to do?