I was going to write that this was demonstrably untrue, but then I saw the muted-microphone shot of an interviewee laughing without context before cutting to a straight-faced interview segment that appeared more natural (at time = 80 s), which was quite possibly recorded after the straight-faced segment to make the video's happy tone consistent: https://youtu.be/N0ng8R0_Tis?t=80

This seems a super-cynical take. Some people are smiley and happy naturally. You might pick them to be in a video.