I have been experiencing the next behavior:
I have a Coordinator with two Routers and two End Devices, all of them are S2C series XBEE.
Using XCTU in Network Working Mode, I see the two devices connected to the Coordinator, but if I disconect one of the End Devices or Both, the still being showing as connected in the Network Graph, with a grey flag betwen them and the Coordinator.
Not the same as the Router, where If I disconnect one of both of them, the left to show in the Network Graph.
As further details, I can say, that in the link shown in the Network Graph shown between Routers and the Coordinator, it shows 255/255, but in the link shown between End-Devices and the Coordinator, it shows 255/0