This is not unique to Illustrator Beta. When I create a new video 1080p file in Illustrator, two artboards are always created automatically, while only one artboard was selected to be created. Therefore, I always have to remember to erase the other artboard before I begin drawing. This is especially important now that AfterEffects seems to be looking at both Illustrator artboards (not just the top one anymore) and duplicates the layers when I import the Illustrator file to composition in AfterEffects. The additional layers are blank.