Passkey is some sort of specific unique key to a device allowing to use a pin on a device instead of the password. But which won’t work on another device.
Now I don’t know if that key can be stolen or not, or if it’s really more secure or not, as people have really unsecure pins.
i tested it on another device, it looks like it gets the passkey from the source device (not from cloud), i had to input the original device’s unlock pattern for it to work
And it’s expected as you still had that device. And it’s not the same key, a new key has been created for that new device. Now if that device cannot be accessed?