George,
Maybe De Carlo never mentioned the spanking because she was terrified that hordes of feminists might descend upon her and lynch her for talking about it.
Actually, she probably never mentioned it 'cause she never thought about it. It's likely that only for us spankophiles do movie spankings loom large in memory. When I finally came "out" to my vanilla husband, I asked him about various movies that he had seen over the years that had spankings in them. Though he confirmed seeing the movies, he didn't recall the spankings at all, even in Kiss Me Kate, in which the spanking is a sort of pivotal part of the plot. He had only a vague recollection of it, though he remembered the story was based on onstage conflict between stars who were ex spouses.
Have you ever seen the posed picture of Gary Cooper being directed by Lubitsch in the scene where he is supposed to spank Claudette Colbert in "Bluebeard's Eighth Wife"? The two stars are posed there, with Colbert over Cooper's lap while Lubitsch looks on and gestures - well, it's decidedly unexciting. Although Colbert is as lovely as ever and is wearing a gorgeous frothy gown, the effect of watching the staging - even though the photo itself is posed - removed all excitement for me. It sure looked like it was all in a day's work for them.
How lucky the star(s) must have been who gave or received a spanking and really and truly was a genuine spankophile.
