Agreed! I loved that too.
If I could chop the movie up the way I'd like, it seems like during the conversation in TTT between Frodo and Gollum, where Frodo says the name "Smeagol" and causes Gollum to remember his name.... That would have been a much better place to stick in the flashback to the Deagol fight.
Oh, for a film editor to hear those words....
Meanwhile...