Wow, that’s an urban legend all right. Totally untrue. Both of Rod Serling’s children are alive and well, and have never been to that building.
My personal favorite theory about ghosts is that they are not the remains of people or their souls, but the emotional residue left over from a traumatic experience (which of course *could* include death). So perhaps Morrison or Hearst—or others less well known—had traumatic experiences there.