Nobody who made the film in 1979 knew that there would be a time when home video was commonplace and obsessive Trekkies spent their lives overanalyzing every last detail.
I agree that the dialogue probably wasn't given much thought, especially due to the film's rushed post-production schedule.
I think it's less likely that the makers of the film were under the shroud of ignorance offered the makers of the television series when it came to realizing that fans would spend their lives belaboring every last detail. Fans had already been in the practice of recording episode audio from television broadcasts for use in (over)analysis. The same practice had to be expected of the feature film -- if not when it was in theatres, then when it aired on television, the rights of which had been pre-sold to ABC before the film's box office debut.