Question on feeding sourdough
I recently received some sourdough starter from someone and so I've decided to try making my first sourdough bread. I've fed it a couple of times, and am keeping it aligned with Hamelman's 125% hydration liquid levain. At this point I have about 8 oz of mature culture. In Hamelman's recipes, for example, Vermot Sourdough, he calls for using 1 oz (2 TBsp) of mature liquid culture, adding 4.8 oz flour, 6 oz water (which comes to 11.8 oz), and letting that sit 12-16 hours, then mixing 10.8 oz of it for the final bread dough. So my question is, is there a reason for only using 1 oz of mature culture and then building that up to almost 12x the weight, or can I just take my 8 oz of culture tonight, add another 8 oz of flour/water (at proper 125% hydration) and then tomorrow just take 10.8 oz from that and be left with 5.2 oz culture that can go in the fridge? Put another way, is it important to bring 1 oz of culture up to 11.8 oz for the actual levain build, or is this just being done out of convenience so that you only have to keep 1 oz of culture normally in your fridge (in order to lessen discards)?
I think my understanding of sourdough hinges on this: is the discard suitable for using as levain or does the actual levain going into the final dough have to be built up specially for that purpose?