The author is mixing different things up and trying to make them one with the purpose of attacking a weakness of the other as if it were the latter. It's one thing to speak objectively and from a rational point of view, but it's an entirely different thing to "be yourself" (personality). One's self could be one which does not filter things and speaks one's inner monologue, or it can be any number of personalities one has as well as "be at ease", don't stress.

Be your self mainly means don't put on airs or pretend to deliver like someone you admire, but rather adapt those to your own style.

On the other hand, I don't think Honne and Tatemae would be constructive in most societies as to many it would become increasingly difficult to read people.