I use a primary which has a tight fitting lid and a airlock. This allows
me to ferment my must to dry before I tranfer to the glass carboy for
clearing. Most people I have come across that transfer before its dry,
either do because they have been taught that way, or they drape a cloth or
cheese cloth over the top of their primary for the yeast to get oxygen.
Also, the instructions on kits are made to be foolproof so they must be very
conservative. That means transfer a little early incase the primary is not
checked on early enough- which probably happens often with our busy lives.
Lastly, Follow The Directions for the recipe. Even though I was taught it
is okay to ferment wine dry in the sealed primary I follow the directions
when doing an expensive kit from WineExpert or RJ. If your still looking
for information there is a forum www.winepress.us that has had this
discussion, do a search and see what others say, every has their way.