At the time the astronauts were fixing the problem, neither they nor Huston knew they were venting oxygen, just fuel. That's kind of a major plot point, a drive

At the time the astronauts were fixing the problem, neither they nor Huston knew they were venting oxygen, just fuel. That's kind of a major plot point, a driver of much of the tension of the movie, and goes a little bit beyond an "embellishment" or "simplification". There are also some other, similar flaws.