Preferments vs AB5

I'm a few months in to a random daily bread baking obsession : ) and have played around with Bread Baker's Apprentice recipes as well as AB5, which to me contrast the kind of two extremes of this hobby, but both result in rather tasty things. I'm now deep into the sourdough forest, hearing different legends around the online forum campfires and trying to make sense of it all.

If yall dont mind, I'd love to learn the "why" of the advantage of preferments, in contrast to just "throwing it all together and waiting a few days".

For example:

1) making a some sort of sourdough preferment (and sometimes a separate soaker), waiting 18 hours at room temp or 3 days in the fridge, and then adding the FINAL dough ingredients

VS

2) "just toss it all together and the yeast and bacteria will sort it all out" which seems to be the AB5 technique.

I guess the heart of my question is, in technique #1, what am I "saving/protecting" that final flour from? Why wait 18 hours to 3 days to add the final ingredients instead of letting it live amongst my sourdough starter and everything else for the while?

From what I understand, the answer to my question is not "to autolyze", since it is not a water/flour mixture that is standing alone in order to do enzyme magic to the starches. My final dough ingredients are in their separate containers during those 18 hours to 3 days.

Is it to minimize the growth of my yeast and bacteria, which would otherwise conquer every little bit of starch resulting in a more acidic / stronger flavor (too strong for some)?

Thanks to all.

-Nick