What the other user says is that maybe those companies will only let 1 device per account to be registered. So you can’t have 2 devices to login. Harder to share.
In this case, Google, that isn't true and just they're mostly treated as special Security Keys ("yubikeys" etc).
To limit it to just one defeats the purpose of all this work. You really will only see that where there is a technical limitation (like... why does AWS only allow a single hardware key per user? If you setup SSO then you can have any number of keys)
To limit it to just one defeats the purpose of all this work. You really will only see that where there is a technical limitation (like... why does AWS only allow a single hardware key per user? If you setup SSO then you can have any number of keys)