I'd imagine that the prohibition regarding drone operations in parks isn't primarily about safety; it's about intrusions on the enjoyment of other visitors, concerns about resource damage, and the potential for the disturbance of wildlife.
Or as mentioned in another post, DJI obtained the video from numerous pilots in the U.S.. And we don't know if they were completed legally (doubtful) with authorized permits. And DJI did not verify same before posting.