I agree with you, there’s probably a lot of epigenetic activity going on in response to environmental factors.

On the other hand, these things can probably be studied and identified. There is an organ shortage for transplantation, which historically peaks in times of peace. One idea is to genetically modify animals to make them more immunologically compatible. I could see a world where being able to control every aspect of the development process allows for more suitable organs (less risk of infection, etc).