Your loyalty to SasuSaku is more than Sasuke's loyalty to Sakura. Some times I wonder why Kishi has not created a character like you in the manga.lol you are being like Shin with the "genes are everything" philosophy. xd
I don't know what is the necessity, Kishi screwing with the fans, I do not support what he is doing and think it is horrible. But I can see him doing it as something for Karin fans to be happy about (Some of them are ecstatic right now), and as a tribute to barren mothers, proving that true bonds are through love and nurture, not DNA.