I appreciate your feedback and very much enjoy your comments on this site. In Oscar Hammerstein's book "Lyrics," he wrote that he specifically rejected "There's nothing more to say" which the women's chorus had sung earlier in the song -- the open vowel-- and chose "talk" for its harsh conclusive "k" sound because that's what Julie would have said. You are correct that many songs do not end on an open vowel and it has nothing to do with character, but in this case Hammerstein made a specific character-driven decision. Sondheim also wrote about this.
