The “words” are the key, not the device. The device should be thought of as a signing device rather than the key. It signs transactions with your “words” and releases then to be broadcast to the network for verification. Backup “words” on metal for security
Discussion
I’m trying to figure out how this works… could you potentially create a key phrase yourself, then add it to a cold storage medium (whether software or hardware), then transfer your Bitcoin to it? Would that be the safest way? And can you use that same phrase in multiple mediums/devices?