She did fuck him. You don't see it in the final cut of the movie, but there were still photos taken from the filming of that same scene featured in a porn magazine geared toward promoting movies released at the time. They're on r eddit if you look up Taboo or Kay Parker. Anyhow, you see a photo from that scene where Kay is most assuredly riding Michael Morrison/Milt Ingley ('Jerry') reverse cowgirl. For purposes of the film, they wanted to show that she was saving her pussy for her son, so you're not far off, b0lxs0p. But it wasn't Kay's decision. The producers/editors wisely cut the intercourse that kay did perform for thematic reasons.
Kay has to be responsible for the sales of thousands of boxes of tissues. Smoking hot body. In every scene you get the impression she's not acting, that she really wants to give her man maximum pleasure. Every guy wants a woman like Kay, but also you'd go crazy after you had her because you know that every other dude wants to bang her. Gone way too soon.
I happened to discover new information concerning this scene. Recently, on reddit, some kind soul posted photos from a porno magazine at the time (1980) used to promote the release of the film. The photos demonstrated just how edited the final cut of the film was because you see Kay in all sorts of positions with multiple actors that you do not see in the film. Two shots in particular were: Kay kneeling to the side of Michael Morrison (the actor in this 2:54 minute clip) sucking his penis; and Kay reverse cowgirling Morrison in which his penis is balls-deep inside of her vagina. So she did fuck him, but for thematic (and likely time) purposes, they left that on the cutting room floor. I hope the footage was not destroyed and, some day, we can see all of the 'lost footage.'
I guess I use xhamster in a more limited manner, pantyhoseislife. Might have something do with being married for a good many years now. Plus, my wife would never be interested in uploading videos the two of us in bed or swinging. But Taboo (1980) is my favorite porno, tied only with The Opening of Misty Beethoven (1976), so if I know any Taboo-related trivia, I like to share it with other people who enjoy the film.
I couldn't agree with you more, mossycleft. To this day, that is my favorite part of any hook-up. Even when it was a prelude to all-night fucking, I loved that descent of an upside down pink, hairy pussy on my face.