

It’s not so much sugar in the flour but amylase in the flour turning starch into simpler sugars. If you add sugar to your dough it means that you’re either not giving enough time to autolyse, or you’re making cake. Either way it’s not proper bread. And yes this also applies to non-sourdough bread. You need a minimum of two or three hours of autolysis for the dough to be nicely digestible and workable on the benchtop, there’s dough conditioners which can imitate part of that but well then you’re getting American “bread”. A typical German process develop the sourdough for about 1 1/2 days, then mix the final dough, let it rest for 2-3 hours (Stockgare, depending on temperature, humidity etc), then form it, then 1 - 1 1/2 hours of final leavening (Stückgare). And it’s not like you can’t get industrial bread over here, it’s just that they’re not taking shortcuts when it comes to time.
There’s regions which add sugar beet syrup, recipes with extra malt (often with active enzymes), or good ole pumpernickel which develops its sweetness through low and slow baking (24 hours in the oven), but adding plain sugar? That’s just ignoble.
I can’t hear you over the sound of UNESCO world heritage.