I could see wanting Mobs in dungeons from the beginning. But they may want us to test for other issues before AI is in it.
For example, it could be hard to give locational error reports of an invisible object or missing textures when you are under attack from AI.
Though other issues could surely arise after AI is added as well.
All I hope is after release when they add new content like dungeons and other "New stuff" unless its balancing of previous known items and dungeons they don't give to much away. Its great finding things without being hand held as to where to look.
This is how it normally works in MO. Even in testing the patch notes will probably not tell us where the dungeon is located.
In previous testing I was in, they tested the systems and mechanics and then built using those outside of testing. So as a tester you seen how things basically worked, but did not test it in every location/situation they used it.
One issue with this method though was that at times it could lead to specific issues in areas that never really got tested. Which could come off as not being well polished/tested.
Hopefully they do a lot of non player testing in later development before release. This would help to maintain the mystery for players and still present a 'clean' game when steam players get access.