What I feel like all the responses missed is that while you're right in that a password-protected private key provides a second factor... what is typically mean

What I feel like all the responses missed is that while you're right in that a password-protected private key provides a second factor... what is typically meant by 2FA is two factors checked by the server. The server has no way to know you're using a password-protected key so it shouldn't really be regarded as a factor.