It wasn't just this exchange. Honestly, I don't really see how he could have handled it better, under the circs, and I don't mean to nitpick.
I hate to out myself like this, but really, my reaction was just kind of a "duh!" female gut response, based on my perceptions of the whole of reported interactions with Mrs. Smiley.
I know he's trying to be as clear as possible while walking the tightrope between pursuing and 'don't let the door hit ya in the butt on your way out', and more power to him. But phrases like (paraphrased), "I almost hope you do leave, because it's what you seem to need" .... the line between detachment and (percevied) indifference is fine. A person might believe and claim she wants a martyr who will sacrifice his well-being and self-interests for hers .... but at the same time, irrational as it may be, there's another little voice crying, "Well .... he really must not care/want me that much if he lets me go this easily."
This is why I find myself conflicted about some aspects of DB. GAL, act "As If", don't pursue, no R talks ... all fine to a point, especially when done in the service of personal growth and autonomy as opposed to attempted manipulation. But any system that encourages systemic deception about one's authentic emotions -- intense and messy and "pressuring" as they may be -- runs the risk of causing a whole new set of problems, however many problems it may solve. IMHO.
"Show me a completely smooth operation and I'll show you someone who's covering mistakes. Real boats rock." -- Frank Herbert