I don't think I even understand this thread.
It's been a couple decades since I saw the episode, but I don't remember sex even having anything to do with this scene. As I recall, the scene was simply Miles being uncomfortable showing affection to Keiko, prompting the two to wonder if their relationship could transcend Keiko's physical transformation. Molly didn't recognize Keiko as her mother and Miles had a hard time seeing her as his wife. I don't think either Miles or Keiko were worried about "getting off." That wasn't the issue, it was how they were going to preserve their relationship and their family, or if they were going to have to readjust Keiko's role in the family. There was no dilemma about whether or not they should have sex.