I don't understand this notion that they are counting towards the eclipse to be honest, why would they do that?
That's literally what they're doing, though. As for why they're doing it, well it's the climax of the story they're telling and also corresponds to its end. It's the most appropriate time to announce anything. Do note also that this countdown's only visual is Griffith's beherit.
they must know that most if not all of the memorial edition watchers are already Berserk fans, so the eclipse is not a suprise like it might've been to the 97' watchers.
These adaptations are typically meant to bring in new fans and rekindle the interest of casual fans.
Imma call it now, we are getting a BLACK SWORDSMAN CHAPTER adaptaion
There's no such thing as the "Black Swordsman chapter".