Well,
While I don't agree with hubby, out of respect for his past, his family etc. I would not push the issue or trick him. Your girls will give full sized eggs soon enough, and he'll be happy to eat those.
For his granmother it was probably a simple reason such as she had too many eggs anyway, and did not consider the yolkless ones to have enough nutrition to feed her kids. Or they were too small to sell or something, and a family habit/ outlook began. These kinds of decisions were made frequently in farm families especially ones that suffered through the depression years. My mother, a thin child, was fed only cream, or half and half if times were tough and my grandmother needed the butter money, in hopes she would grow and thrive. You can imagine what happened when my family found out I was giving my babies SKIM milk on occasion (they lived).