What's the point of long/complex sourdough feeding techniques? About a year ago, a friend taught me how she makes her sourdough bread and gave me a portion of her starter.  It works great and makes fantastic loaves.  I've started to look at other recipes online and in various books (e.g. Flour, Water, Salt) to better understand how different types of sourdough breads are made and I've realized that the splitting/feeding of the starter in my recipe is quite a radical departure from every other Levain/sourdough-starter recipe I've found.  Otherwise, it seems to be the standard high-hydration (78%-80%), autolyse (2 hr), bake-in-a-dutch-oven approach that's so common these days.

Specifics:


I typically only have time to bake once a week, so I store my
sourdough culture in a glass jar in the fridge.  
For most of the past year, when preparing my dough I would simply
take the starter out of the fridge, split it, and dissolve both
portions directly in warm water (~90 F).
The starter would then get some flour and be put back in the fridge
(100g starter, 100g water, 100g flour).
The portion for the bread would simply have the flour and salt added,
autolyzed with occasional folding, divided and allowed to rise
overnight (~12 hours).


In contrast to this simple approach of dissolving the starter directly in water and then adding the flour for autolysing, every other recipe I've found seems to require a 12 or 24 hour pre-feeding routine that involves feeding the starter first, then discarding most of this newly fed starter before adding this "revived" starter to the water/flour before either a long bulk fermentation or a long rise time.  Or some even require multiple feedings...

Why do people spend so much time and energy on long drawn out pre-feeding routines?  My approach obviously works - the bread rises just fine, the crumb is fantastic (that's mostly due to autolyse and cooking in a dutch oven), it develops a nice flavor and a little sourness over the 12 hour rise time (especially if it's a cold night).  

What am I missing?  Better flavor?  I can seen an argument for getting the culture more active this way, but I don't see much difference between that and simply allowing my culture to warm up to room temperature. In fact, I've started letting my culture warm up before splitting it this past month, as well as leaving the newly fed cut at room temperature for several hours before sticking it back in the fridge - however, I haven't noticed any difference in flavor nor in how long it takes to rise, etc.
Absent a definitive answer here, I'm going to take a stab at this based on some experience I had with difficult sourdough starters.  Note that I make a lot of sourdough items but do not do any kind of multi-stage prefeeding ritual.

Sourdough is a culture of multiple types of bacteria and wild yeast.  Sometimes wild yeasts do not reproduce rapidly or produce as much carbon dioxide (for leavening) as commercial yeasts.  I've definitely had the problem before with a starter that it wouldn't produce anything other than a superdense bread, no matter how long the dough rise.

Most of us keep our starters in the fridge (unless we run commercial bakeries).  Thing is, at fridge temperatures, the bacterial culture will grow, albeit slowly, but the yeast will hardly reproduce at all, and will produce no carbon dioxide. So, when you take it out of the fridge, if you use the culture immediately you may have an imbalance of active bacteria but sleepy yeast (this is some inexpert armchair biology here, so a big pinch of kosher salt with it).

You are solving this via the use of 90F water.  I solve it by proofing a sponge for 7-12 hours.  However, there are clearly sourdough aficionados who feel that this is not sufficient to restore the yeast to full strength and that it needs more time and feeding.  The feed, split, and discard routine I believe comes from commercial bakeries that never refrigerate their starters because they use it every day; it is the advice given in the Berkeley Cheese Board's cookbook, for example.  Doing this over 36 hours or so could be assumed to get the sourdough into the same state it would have been for a sourdough kept constantly at room temperature and rotated every 24 hours, allowing you to use the exact same rising times/temps as they would use.

Now, back to my all-natural wild yeast starter that wouldn't rise very well.  I did not try feed-and-split for 36 hours; maybe that would have made it rise adequately and is the reason for this technique.  Instead, I started the starter-making process over and got a better strain of yeast the second time.