What the other person is trying to explain to you is that your Yubikey solution fails the following scenario: you leave your laptop at school. With TouchID, no

What the other person is trying to explain to you is that your Yubikey solution fails the following scenario: you leave your laptop at school. With TouchID, nobody can unlock it. With a Yubikey in the USB-C port, anyone could unlock it. That's why macOS Yubikey login integration requires you to type in a PIN on the lock screen. At which point it's no different from typing in a password. Not equivalent to TouchID at all.