When Rean and Kentucky arrived at the continent where they could find a Long-Distance Teleport Formation, they didn't go there straight away. Instead, Roan and Celis called the two back into the Dimensional Realm. "We have reached the limit of the Late Stage of the Elemental Space Realm. It's time to get another breakthrough."
Let's not forget Rean spent five years outside using Spatial Gates to travel, only coming into the Soul Gem Dimensional Realm to recover his energy. During this time, the Soul Gem Dimensional Realm was still running at an accelerated pace while Roan, Kentucky, and Celis cultivated.
