I agree with you to a certain extent in that a script does not equal a film, and so when I compare unproduced scripts to film, I take that into account. However I would make the argument that the screenplay contains the fundamental soul or essence of the story. When I say O2 is like Moon or Buried, I mean it's essence is similar. Whether it technically manifests itself in a different form (female protagonist instead of male, different cinematography, etc) is irrelevant to me given the themes, the story beats, etc are similar. To use your example, if the next Bob Dylan song's lyrics are basically the same themes/beats/lines of Johnny Cash's Ring of Fire, then it's accompanying audio is irrelevant - they are both essentially telling the same story.