If the Vivre Card says that Kuina was born in East Blue, then she was born in East Blue and not in Wano.
Even tho it would be great to see Zoro as a scabbard, Koshiro' substitute, Kuina's Vivre card says both (Kuina and Koshiro) were born in East Blue. In my opinion, it makes no sense to believe that Denjiro is Koshiro just by the fact that we know Koshiro isn't an orphan and the fact that Denjiro is an orphan is enough evidence to believe that Koshiro can't be Denjiro. I don't think Oda intends to reboot the Vivre card's info.
Just my opinion tho...