Siebren will allow Seto to set the pace - Seto is the one who needs assistance here, after all.

He shakes his head - he has not made himself clear. "Would you believe I am not worried? This is the first time I have chosen to be Sigma without the decision being...forced, in some way. I had the option to continue to herd people to evacuation, or to evacuate to the train myself, and I chose to hold the line knowing full well that Sigma would be required for me to succeed. It is...freeing, in a way I had not expected." Sigma had begun as a coping mechanism necessary for survival on missions; that he could now be an option, one tool in a set, is a development that Siebren had not foreseen.