This is all sort of pedantic but the way I read the situation is that the only authentication is proving that the entity on the other end possesses the private

This is all sort of pedantic but the way I read the situation is that the only authentication is proving that the entity on the other end possesses the private key associated with a certain public key. The authorization part is two fold: is key X authorized to access account Y. And then it's passed on to Gerve for more specific authorization checks. Having implemented such things, I am probably thinking more about the internal situation, sorry..