I disagree. Even if you use the same device to access a service, you still need the device to authenticate. It's authenticating by more than one factor. You

I disagree. Even if you use the same device to access a service, you still need the device to authenticate. It's authenticating by more than one factor. You need my password, plus my phone, plus possibly a way to access my phone (my PIN code or fingerprint). That's much better than just a password.