What makes me say that was the cinematic which was listing your choices you've made during Act 1 while the main character was sailing towards Grymforge.
Wich is gone now ... so ... ?
Also above ground there is the Mountain Pass which clearly separates Act 1 from Act 2
Or simply separates two locations with loading ... just as surface is separated from Underdark?
which you can't pass at this current moment in the EA.
Since its not yet done?
Those were clearly the end of Act 1.
They added Grymforge just because someone found a bug before how to pass through the lake and enter that zone which had been normally restricted until that moment and also to add new content.
That dont explain why they waited so long to add it, since that bug was discovered back in patch 1 or 2 ... meaning more than year back.
Also, as far as i know by simmilar bug some people get inside that Shar temple ruins ... and yet they didnt include that.
Isnt easier explanation here that it was simply ready just now rather than before?