As an old timer here (!), who saw the OBC tryout at the National in DC, senior year of high school, I can attest: the song has always landed as a sexual metaphor, though the original staging trusted the lyrics -- and an unknown named Betty Buckley -- to sell the provocative imagery. It was naughty when I was 17, and has held onto its whiff of naughtiness even when limply and asexually filmed. I've said before, it's a number that carries its weight -- sexual and theatrical -- in the soaring melodic line, originally in every way thrilling via Buckley's pipes. It just doesn't work with anything less than a raised roof. The film made it, of all things: merely sweet, despite the fadeout on a clinch. I'm all for romance, but the erotic heat between Jefferson and Martha is part of the plot, if not perhaps history.
Once I owned the vinyl OBC, I always presumed the lyric was a foreshadowing of Martha's shortened life. The show as written by a history teacher, and he played that card in the lyric, yes?