Just speculation on my part since Epic appears willing to use different exclusivity contracts for early access games. Hopefully I'm wrong though, especially since something like Darkest Dungeon 2's first year of EA will be in October and I'd like to actually grab that one when it comes to Steam.
Darkest Dungeon 2 is exclusively for early access, so if the game takes 19 months to get out of ea, it will be 19 months exclusive.