My interpretation of the quote is that Jane Austen has a tendency to present the self-deceptive character (such as Darcy, Sir Thomas, Emma, and Tilney) as a technique to do indirect discourse into the internal changes that their lives will encounter as dynamic characters, and ultimately to convey how their lives and storylines will transform them.
Emma should be added to the list because she is also self-deceptive, that means, she is portrayed one way, but we also know that the image that she has of herself will contradict her. This is evident in Emma's insistence that she will not be married, yet falls in love and ends up accepting that her entire vision of herself as a different, and independent woman who is not drawn by emotions was all the story she built about herself.
Sir Thomas's own self-deceptive story is that he is a philantropist, and a great public servant. Yet, we also know that he is in love with himself, and that the things he does are only more ways to feed his ego,of which he is quite keen.
Darcy's story of self-deception is clear from the beginning, where his haughty attitude to everyone else is simply his way to say that he is above the entire world, that he does not like dancing, that Elizabeth is too plain for him, and that he hates the country. What we find is that he ends up succumbing to his feelings for Elizabeth, and does a clear 180 change helping Elizabeth sister, and becoming quite a teddy bear in comparison to the absolutely obnoxious first impression.