I agree on the importance of this scene in the development of movie-Gollum.
But the way the scene was in the theatrical version was sufficient, I think. When I watched it for the first time in the cinema (without book knowledge back then) I found the reaction of Gollum comprehensible. He feels like he is tricked by the first being in centuries he thought he could trust. It made perfect sense to me.
And realism is over-rated.