I apologize, I hadn’t realized that this conversation was due to you not being a native english speaker.
Yes. “In someone’s shadow” is connoted by someone appearing both behind and lower than the person casting the shadow. It is not a synonym for merely being behind someone, but is used to convey the idea that if there was a source of light, say from the sun, the shadowed person would have the light reaching them completely blocked.
In this case, the person behind being around the same hate and, in fact, slightly taller, cannot by any reasonable reading of the image be symbolically representing him being in the woman’s shadow. No matter how small he was, his top line extending beyond hers completely eliminates that reading as valid.
Yes, this is a good explanation of how the first one has the woman cast in the man’s shadow, but the second one does not have the man cast in the woman’s shadow.
This one is better than the other because no one is in anyone else’s shadow in the image.
All of the following effects can remove the “shadowed” nature of an image:
Moving the person behind far enough away towards the back.
Moving the person behind far enough to the side.
Making the person behind larger in at least one dimension (which is what was done here).
Placing the person behind higher in the image.