Devices appeared in the application for 30 seconds, and then disappeared. This time is enough to send a signal to the device, delete data from it and make a route to it.
On which operating systems the devices worked, it is not known. The author suspects that on iOS 12, since mostly elderly people live next to him.
Some commentators have suggested that these are phantom icons, not real devices. This is possible, although enoughowl10 is unsure of this.
Apple has already contacted the person who discovered the bug. The company will probably fix it in the next beta version. [Reddit]