I'm replying to the OP, even though I suspect the OP is not reading these anymore.
This is not a glitch with Windows. This is in fact by design.
Windows Connect Now searches your network not only for devices that are currently connected, but also for any devices that may potentially be capable to being on your network (if you give them permission.)
These ghost devices in a sense have been on your network, and are continously so. Here's why: Phones and some other WiFi devices, but especially phones, are continously scanning for available networks, even when they are connected to one, to try and find possibly a better one (there's some technical babble of what's they are doing, but basically in laymans terms this is the best way to describe it.) Because of this, your WiFi network is continously being scanned intermittently by these devices, and your WiFi network is acknowledging of course that it is available. This will even occur if your network is a hidden one by the way. This is how a phone (or any other WiFi device for that matter) can actually even begin to connect to a WiFi network.
When you are out and about, and you may need to connect to a WiFi network at say a friends house, or Restaurant even, you first have to pull down the list of available networks to actually connect to it. If you ever notice, depending where you are at that time, there usually is at least one more, and often times, numerous other networks besides the one you're trying to connect to available. Most of the time those devices are listed very quickly for you. This is not because your phone is the fastest searcher in the world. This is because in the background while you were doing other things, or it was in your pocket, it was also searching the area for these, so it could have it available to you at a moments notice. This feature on some phones can be turned off, and those wishing to save battery power even more may look into that, however, that for another post.
The thing is, in order to get the device list, the phone/device sends out a 'packet' of data requesting devices info, that other WiFi devices and routers recognize, and respond to with information that is appropriate, in the case of a router for instance, it SSID (the WiFi network name) and type of security challenge that will be needed if that device wishes to join. The initial sending out the information will almost always include it's MAC address, which is USUALLY assigned to a Manufacturer. I could go on and on about this, however, it's Googly information that is even longer winded than I am.
With Windows Connect Now, it goes and does some further work so you don't have to. It's does similar to what the phone does when you click on the Network in your 'File Explorer', Windows Connect Now, sends out a 'packet/beacon' to not only get a list of the current devices connect to your network, but also 'POTENTIAL' other devices that respond back to it's request via whatever WiFi outlet was available to send the beacon. Also, it reads the logs you usually can not see yourself from a router to see what has within a certain amount of time send out one of those packets, to try and give you the fullest list available of all possible devices you may connect to, if you, and that device BOTH have the proper authority to do so. With Windows Connect Now off/disabled, you only see the actual devices that are currently on your network. In this regard, WCN is not necessary as a feature, so it does not hurt at all to have it off, however, it does make it convenient when you want to connect to a tablet or other WiFi device that really is on your network, or at least you want it to be, then it shows you at a glance if the device itself is at least throwing off it's own beacon.
I know this is long winded, sorry for that, but hopefully in it's entirety it will help someone understand why they see these devices.