It would have been nice to see that scene, for sure, but I don’t think it was necessary. Like you said, he’s so raw when he says it, I think it really drove home how much they meant to one another and that they honestly did promise to take care of each other. It was these two against the world. That’s what made it so heartbreaking for me.
That whole bit where Neal is like “2 years?! Where were you the rest of her life!?” You can just see it in his face and hear it in his voice how much he loves Emma and how pissed off he is on her behalf that she’s been alone until he entered her life. Love it.