I can state for a fact that these are not excerpts from the movie. Indeed, they just let you know about as much as you'd know from the pilot and an episode or two of Firefly. Heck, if you've seen the trailer, you know more about where River is now than these clips reveal. Certainly if you've seen the show, you know the information disclosed in these clips.
Still . . . it's excellent backstory. It shows us things we've only heard described. And they're sad, creepy, touching, and horrifying.
Captain Reynolds, you were right. It may have been the losing side, but it surely wasn't the wrong one. Not when the Alliance can do what they did to River Tam.