Yeah, I'm a little intrigued by this as well, to me it feels like there's something hanging in the air. Maybe it was just about realizing what Mab was doing, but the conversation is not really about Mab. By the context, though, how IDHarry speaks about being with Lara as some sort of positive, I'm inclined to think that Harry was missing something good about her?
But I dunno, IDHarry has also said a bunch of things that are not necessarily right or a reflexion of what Harry wanted or should do, like the thing in Skin Game about him waiting on Molly.
I'm also intrigued by the fact that, if I'm not forgetting something, this is the first time Harry sees IDHarry outside a dream, for the first time, Harry was effectively awake when they have this conversation.