Edward and Elinor are said to be attached in chapter three. Her mother "loves him already" in chapter three. Elinor gives him high praise and Marianne considers them engaged in chapter four. Meanwhile, we still haven't heard him say a single word! They are separated in chapter five, and then he speaks (to ask where the Dashwoods' new house is).

In fact, Edward is such a non-presence in the very first chapters, that filmmakers have practically no choice except to compensate with scenes that are not in the book. There are no scenes in the book. At all.

I don't want to step in Austenuations territory, so I'll just say that in other novels, we usually get some dialogue and characerization for the hero, so why don't we get any here? I don't think that Austen was still mastering her craft, because Northanger Abbey preceded Sense and Sensibility and the hero of that novel is very well fleshed out. So, she must have done it on purpose. Of course, these are still the early chapters, so Edward may get character development later.