The quiet parameter is documented as not logging "connection events".

On a server with SSL enabled, if you were to connect without using SSL the following is still recorded to the log:

I NETWORK  [conn1533713] AssertionException handling request, closing client connection: 17189 The server is configured to only allow SSL connections

I think this class of events should be covered as a benefit of quiet is reducing log noise due to connections opening/closing out of the servers control.