Haha, you noticed that too? I think it's a little too much for the H/Hr fans to hope for, tbh. I'm guessing it's just because Daniel and Emma have the most chemistry out of any of the four actors, and it's only natural they display their strongest scenes in the trailers. So yeah, I don't know how much of that earlier subtext was intended - perhaps when the writers also believed that H/Hr might happen? - and how much was just a result of those two. It was really Dan and Emam that made me ship them, more so than the book characters. :D