FYI - "To be announced" means that this game is in the Alpha/demo stage and not in the "Early Access"/mostly playable stage! Those downloading it should consider it as a "preview" of a game that may be worth looking into!
There have been varying opinions about the game's current status and it is still unknown as to when Epic will release the Beta ("Early Access") version of the game on Steam, let alone the final version. Epic Games released the game on January 26, 2023 on its own distribution (or storefront) service but states in the game's page under "Additional Notes" that the game is "still in development" instead of in "Early Access" (Epic Games also has their own "Early Access" designation for games). IMHO, all of that makes it sound like that this is an Alpha version of the game. I guess that you could call it an "Epic time exclusive" as you've put it, with an indefinite length of time until further notice from Epic Games.
The way this game is described, it leads one to believe that it has some interesting new mechanics where you control 2 characters at once and that is part of the challenge. But no... Plays like any 3rd person shooter. Meh...
https://www.youtube.com/watch?v=Ex9GHFILaCY
Shoulders of Giants 4K PC Gameplay