One of the complaints that someone posted on the blog was that Batman reads more like Bruce than he does Dick
I think it can easily be read as Dick emulating Bruce's way of talking. Certainly he knows Bruce well enough to do so. And the Robin's pretty clearly Damian (or at the very least, not Tim. Even more not-Tim than that other preview. You know, set in Madrid. The Gotham of Spain. Yeah. Sorry, digressing.)
Anyway, I don't think Dick really wants it widely known for certain that he's a different Batman, and certainly if he approaches this conversation as Dick, Harley's gonna know the difference. Isn't she supposed to be really good at analyzing people, or is that a long-retconned-away incarnation by now? Either way, given the number of encounters she's had with Bruce before, her not immediately calling Dick a fraud is a decent endorsement (unless she does so the page after he leaves, anyway).
The signal goes on and he shows up. That's the way it's been, that's the way it will be.