Man, I forgot how much I loved the line "I'm not a twin anymore."

Elan realized what Tarquin wouldn't: Tarquin just isn't that important to the story. He's not the bad guy and Elan didn't want him to continue having an effect on the Order's actions. Additionally he knew that Tarquin would survive the fall, and that a captured Tarquin would be an escaped Tarquin within a strip or two.