Like on a hardware wallet, you sign the transaction on the device and only the signature goes to the computer and then to the network. In nostr you do the same with this device. Instead of a transaction, you sign the message you are posting.
Of course a bitcoin transaction is more important than a nostr message, but for a thing like a social platform, no one can hack or steal your account.
it seems like it would be important only if i want to make absolutely sure that no one else besides me was posting on my account
Yes, also the login process is automatic as long as the device is pluged in. Password managers can achieve that, but it might be more work if you wanted to port to another machine, or change browser (in case of passwords saved in browser). It is very similar to what Yubikey does.
