In John Updike's "Separating," what is the significance of the kiss Dickie gives his father "on the lips" that is as "passionate as a woman's"?

At the end of Updike's story "Separating," Richard tells his son, Dickie, that he is separating from Dickie's mother. Dickie is the last of the four children to be told about the separation, and he accepts the news calmly. When Richard says goodnight to his son after Judith (his wife) has already done so, Dickie kisses his father passionately on the lips, like a woman.
The significance of this kiss is that it is a proxy for Richard's connection with his wife, Judith. At the end of the story, Dickie whispers "Why" into his father's ear, trying to figure out why his parents are getting divorced. The last line of the story is "Richard had forgotten why." Richard has become distanced from his wife, and they want to separate after a long marriage, but he can't even recall why he wants this separation. He now must communicate his affection and love for his wife through his children, as he will no longer be connected with Judith. His son's passionate kiss stands for this missing connection between Richard and Judith and for the communication of their love through their children. Even though Richard and Judith feel distanced from each other and will soon be physically distanced from each other, they have this one last symbolic connection through their son Dickie.