Larian's games are always 3 Acts. What people call acts and what they call acts aren't always the same thing. People seems to split DOS2 into 4 acts based on the maps, but Reaper's Coast and Nameless isle are a single act to Larian.
They are narrative driven too, so it's not hard to speculate that Act 1 ends somewhere around the Moonrise Tower or soon after you deal with the place. Act 1 will end when the "remove the tadpole" quest will be completed and replaced by something else.
Anyhow, the EA doesn't have the entirety of Act 1, just most of it. This was confirmed last week by one of the game's writers.
