Originally Posted by The Joker
What do you mean could have? He didn't say anything about it. That's the point. It wasn't mentioned to fool people into thinking he had died. The question asked was why didn't he tell Selina about the auto pilot in the first place.
he doesn't tell Selina because he's about to try to get rid of a nuke and he's not sure he actually will make it out of the blast radius or if the autopilot will fail, etc. He's not about to give her the same false hope that kept him crippled emotionally until Alfred told him the truth haunt Selina. And also for the obvious crippling of the dramatic effect. If you talk about the autopilot, it puts the seeds of doubt in the entire audiences mind, thereby losing any emotional impact.
Also, to the claims that he didn't have time, I mean come on, it's editing, we have no idea when exactly he left, when he engaged the autopilot, when he has that final moment of acceptance, etc. Brilliant misdirection through editing that clearly worked very well considering the reactions from people. I myself was nearly in tears.