That section was for the discussion of the actual game beta (version 0.x) not for the beta of a revision. You can discuss the current beta revision in the general discussion forum.
The arcade beta is not the beta for HotS. The beta for HotS should be version 2.X while last I heard the arcade was just a big patch (1.5).
You can write whatever articles you want as long as they are appropriate to the section (about StarCraft II). Do not expect them to be made new articles though as the administrators control that.