[ambivalence]

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.