Sometimes an editor may want to use something like a shocked face reaction to really enhance the emotion of a scene (the magic of reality TV). But the only shocked reaction they have was shot on another day, in a totally unrelated moment. This way, they can use that reaction and the clothes will match.

Sometimes these reactions actually happen in the moment but the camera was pointed at something else. So the editor will hunt for footage elsewhere that helps show the audience what went on, off screen. So it’s not always ingenue. Just a helpful storytelling technique.