Well I agree. Glagolitic became the official scripture at the end of 10th century. But as south Slavs accepted it earlier (end of 9th) century it could be possible that some Kievans at least came into contact with it. But that's entirely conjecture.
My point was that Greeks have influenced Glagolitic (well to a certain extent they gave it to us), but they couldn't have influenced pre-Christian Slavic writings. Neither could the Romans. Slavs appeared rarely in Greco – Roman literature