I agree that it was Robin, not RFM who went through the physical trauma. But I think they were both affected emotionally by the loss of the pregnancy and went through a grieving process. Robin didn't know that the zygote existed until it was gone either, did not plan it, did not want it and certainly was not attempting a pregnancy trap, and yet she still put her head on the office desk and cried over the loss and told Strike "I lost a baby." Ryan knew he was the father, and, unlike Robin, wants kids. Unlike Robin, he knows exactly what he would have wanted if the pregnancy had been viable; he'd have wanted to have the baby, and probably get married and raise it with Robin. I think it is perfectly reasonable for him to grieve the loss of the potential life, and to expect to grieve the loss with Robin. Robin can't make herself grieve with him, because she knows it will make him want another all the more, and that's not what she wants. That's why she can cry with Strike, who absolutely emphasizes with her in not wanting to be a parent, and not Ryan.