That is why potato chip bags say sold by weight not by volume. Think about most things you
buy. When you
buy say a gallon of milk or bottles of soda they leave a rather large area at the top of air. The reason this is done and bottles are made for most uses is to allow expansion from either heating or freezing. So the bottles we get our liquid in are made for other things then nicotine. Imagine how ...... off you would be if you forgot that gallon of milk or bleach in the back of your car and you lived up north and it froze and busted in your car. The bottles being bigger do have a pratical purpose.
I think the fact that what we use and "oxidizes" turning color is the greatest thing for the consumer because of this and how we like to complain as consumers the vendors fill to the top to avoid as much air so we win. When you buy a 30 ml bottle from company x and it is filled to top you are actually getting 32 ml or whatever the engineer decided was the safe expansion of that bottle.
Air compresses easier then liquid does. That being said I would be careful leaving that bottle that is completely full to the top sitting in your car in the middle of summer while living in Arizona. You might come back to a bottle that has the leaking liquid all over your dash.