My first response was "origami birds? Denizens don't usually exit their cars. Kind of Deux ex Machina."
But after a moment I realized, it's thematic. This whole season has questioned the worth of denizens, whether they were a good thing or bad. In prior seasons, of course we saw Atticus joining Tulip's journey, and Lake becoming a member of the real, non-chrome, non-train world, so we as the viewers already knew that.
But I think it was more for Grace and Simon to see that the denizens have worth and purpose and individuality enough to make friends with. Hazel's funeral for Tuba must have stuck a foot in that particular door, but the saving via origami birds Grace had restored clearly show a sense of gratitude and loyalty.
Not to mention: Throwing someone off the cliff they've been avoiding for three solid minutes of fight sequence sure works to shock the emotional system though, and then of course bringing them back is that Moment of Relief every good story must have.