Glory to Jesus Christ!
There are some problems. The view that the Scriptures should only be in the “Holy” languages, defined as those that were on the sign placed above Our Lord on the Cross (Latin, Greek and Hebrew) was held by some in both the East and the West. The order of the events of the mission to Great Moravia is also a bit different than described. There are several other problems. I would suggest looking at some of the books on this topic such as “Cyril and Methodius of Thessalonica, The Acculturation of the Slavs” by Anthony-Emil N. Tachiaos
Fr. Deacon Robert