Levain vs Culture

Many of the sourdough recipes in "Bread" and "The Rye Baker" start with a levain or sour (sometimes as many as 3 for rye) which resemble a culture refresh feeding - a small amount of culture plus flour and water.  

OTOH, the CIA Baking & Pastry textbook sourdough bread recipes usually call for something like 20% culture in what resembles a straight dough in procedure.

I'm guessing that if you don't use the levain to change the composition (ie, types of flour) or hydration (liquid to stiff or vice versa) then it doesn't make much if any difference.  Use the last refresh feeding to build up your culture (eg, 14g or 28g of rye culture fed at 1:10:10 instead of the usual 7g) and use 200g of culture instead of a levain.   

This approach might have some production advantage in a commercial bakery.  But "Bread" is aimed at professional bakers and gives recipes in commercial as well as home quantities, with levains and rye sours.  

Is there some difference in the outcome that I'm missing?  Or is the CIA method just a way of streamlining higher volume production?