Winemaker
Thinks s/he gets paid by the post
I've read that one of the advantages of boxed wine is that as the contents are consumed the plastic bag prevents oxygen from getting to the wine and altering the taste, at least until you have to let some air in to get the last of the wine out.
I have no idea whether that is true.
You hit the nail right on the head.
The infamous "sulfites" that are put into your bottle are antioxidants to prevent oxidation and browning. The amount put into a wine is based on the acidity or ph, there is a formula/chart if anybody wanted to google it, they are in parts per million.
The plastic bag collapses and prevents the O2 from doing its thing. When a winemaker makes wine, he wants the yeast to get O2, but after fermentation, everything is done to prevent O2 from coming in contact. A small amount is absorbed while aging in a barrel. After a bottle is opened, dry reds ARE to be aerated and exposed to oxygen to INCREASE the flavor.
If you don't finish a bottle, then all attempts to prevent O2 from entering should be employed.