What is the significance of sex scene in Batman: The Killing Joke?

Question

In Batman: The Killing Joke, they showed an additional story involving Batgirl which was not even present in the original novel. This was not a bad idea as it gave more depth to Batgirl's character. But Batman and Batgirl's sex scene looks a bit weird to me.

I do remember Bruce Timm hinting at a Batman/Batgirl relationship in the DCAU (DC Animated Universe), like in Batman Beyond A Touch of Curaré

Terry: So you and Dick Grayson like, dated.
Barbara Gordon: In college. Puppy love. Later on, we just never talked about it.
Terry: (Eating doughnut.) People should communicate more.
Barbara Gordon: Dick finally got fed up living in Batman's shadow. He decided to leave. He was hurt when I chose to stay behind with Bruce.
Terry: As his partner. (Gordon's grin widens.) His girlfriend? (Gordon's grin widens even further, leaving McGinnis shocked.) Whoa!
Barbara Gordon: On the street, it was like ballet. We were the perfect duo.

And it was also hinted in Batman: Mystery of the Batwoman. But it never appeared on screen directly.

But this sex scene came out quite awkwardly to me, what was the point of this sex scene? Was that a nod to DCAU's hinted love angle? Did any of the officials confirm anything about this idea?

Answer 1

The answer is "character development":

The creators have said that an entire prologue focused on Barbara, including her sexual encounter with Batman, was included in the film to develop her character in a way that the comic failed to do. “It was really important to us to show that both of the characters make some pretty big mistakes. I mean, his “parental skills” aren’t that great,” artist and producer Bruce Timm said in an interview with Vulture.

http://time.com/4420487/why-people-are-upset-about-the-batman-the-killing-joke-movie/