I thought it was new at first as it wasn’t on the list of branches I pulled on April 20th, but it turns out it has existed since 2020 and was first seen right before the game came out. Since then it has only ever been utilized for about 1-2 weeks prior to each of the civilization DLCs releasing, and was last seen with Knights of the Mediterranean.
Presuming the branch is used for granting early access to media outlets or similar effect, it could be heralding a new civ DLC like it historically has been, or perhaps something else that is changing the face of the game and needs promotion like the “Age Pass” datamined on AoE II’s PUP.