I guess the purpose of this is to have us prepared for how Adam is gonna be portrayed in Ignite Me -- which according to the blurb is wrong than what Juliette thought of him the whole time. It's sad and unfair, really (even if I'm glad that it makes Warner x Juliette 90% endgame).
Or maybe this is to rile up readers, so in the third book, Adam could redeem himself. And that would be the element of surprise in the plot? lol I don't know.