It means that whoever hasn't Jaden/Yubel still unlocked, the Skill we get from this event will be in the Box in October, probably along another chance to unlock him.
It also means that the actual group of translators must be working on the new world, and whoever is left in charge must have made a half-assed translation of the original Japanese ad with Google. I've seen kindergarden texts with better grammar than this.
yeah they word it weirdly, but it's saying you can get the skill from a character if you unlocked the character from the event that allows you to obtain said character in case you don't have it.
Slime world (arc-v) is another similar plot. Usually YGO deals a lot with virtual, fake realities (Bakura's RPG, the rapture of Jaden's Duel Academy, etc).
The Duel Monster world that the academy is temporarily transported to in GX is a real reality, though. It's more like another reality than a fake reality.
if you are talking about the reality in which hasleberry is a rastafarian tyranosaurus, then you might be rigth, it might be... authentic reality and not fiction.