I think I see what you're saying. My biggest question would be why do this if this isn't going to be a full fledged spin-off? You'd have to follow Sarada's conflict until she gets closure, which might not be until a couple years from the Gaiden when she's old enough to grasp everything.
I have a funny feeling that this is a set up to drive Sarada to greater eye power. Since this era doesn't know war or even much conflict, she wouldn't have much of a chance to develop a strong sharingan (the traditional way). Orochimaru was there for the whole explanation of how the Uchiha Curse worked, so it's not out of the question that he possibly set it up to push the kid to eventually the same level as Sasuke. It's either that or that isn't Karin's DNA, for all we know that could be Sasuke's. In which case all it did was match her set of DNA that matches his set. So the only thing displayed is what matches (hence why the graphs didn't change).
The second biggest question that needs to be answered if this is all true(and for now, lets say that it is).. is why Karin would allow Sakura to take care of her child. I would think that Karin would be an over protective mother to her kid, especially if it's the only thing connecting her to Sasuke. Was it because Sakura was unable to carry a child? There are some big questions kishi needs to answer before the Boruto movie is out next month.. he better answer them good.