As I just noted, you are absolutely 100% incorrect about this. There are plenty of realtime cutscenes and DF themselves point this out. Again, the framerate tells the story.
The realtime scenes have variable framerates, the pre-rendered scenes do not (they run at 25 fps exactly).
They BOTH struggle with that scene. The framerate dips as low as the teens. There is no texture pop-in present in the game because the game doesn't really make heavy use of data streaming (which is why each level is loaded separately and of middling size).
That scene is realtime. At the very end of the scene, after the jump, it jumps to a video and shows Gabriel walking with a map behind him showing his progression. You can see the moment when it switches from realtime to pre-rendered even (quick black screen).
Besides, you can actually SEE compression artifacts in the pre-rendered videos. They can be subtle, fortunately, but they are there.
Also, let me ask you this, if these scenes were video clips, why would the framerate vary so heavily between the two versions? Especially when DF has proven that the file sizes are exactly the same. I shouldn't even need to ask this, really, but it further proves my point.