A good rule of thumb is that TV and movies are not like books. A book can be the singular vision of an author (filtered by editors) but in film the process is typically much more team-driven.
There's an old axiom in Hollywood (actual provenance unknown, but often attributed to Kubrick or Hitchcock) which goes "Every movie is written three times: on the page, on the stage, and in editing." Each is an act of adaptation, so there's rarely an original "vision" which survives the process. So really, the script (and which draft you have) is just a departure point... what the writer wanted/or was instructed to do at a given point in the process.
Thus, the Grissom was destroyed so easily because the final decision was just to go with "Lucky shot, sir," without any reference to shields or what have you, and we are left to draw our own conclusions, regardless of what the scripts said.
There's an old axiom in Hollywood (actual provenance unknown, but often attributed to Kubrick or Hitchcock) which goes "Every movie is written three times: on the page, on the stage, and in editing." Each is an act of adaptation, so there's rarely an original "vision" which survives the process. So really, the script (and which draft you have) is just a departure point... what the writer wanted/or was instructed to do at a given point in the process.
Thus, the Grissom was destroyed so easily because the final decision was just to go with "Lucky shot, sir," without any reference to shields or what have you, and we are left to draw our own conclusions, regardless of what the scripts said.