Wow, nice crumb! On reflection, I think I read about the folding method a long time ago. Twenty-three hours sounds doable - my count includes an additional 12 hours for an overnight refresh of the starter.
Sourdough comes in all shapes and sizes, depending on the yeast and microbial cultures in the starter and baking environment. The well-known San Francisco style is atypical; in fact, I think it employs sourdough just for flavor, introducing commercial bakers' yeast to leaven the bread (there's a French baker's term for this flavored sponge technique, but I can't think of it now). There used to be a guy who actually sold freeze-dried sourdough starter cultures through the mail from various locales around the world (Egypt, Norway, Alaska, etc.) for not too much.
I made my first starter from scratch about twenty years ago and have baked with it more or less weekly since, making new starters along the way with rye and buckwheat flour, and with Egyptian wheat when we lived in Cairo. This bread is extremely good (as you point out), and really only takes about 20 minutes of actual work. You can also use sourdough to make croissants, pancakes, crusts, whatever.
I'm doubly intrigued by the folding technique now, as the only tedious part of making the bread is beating (actually I beat more than knead) the wet dough to develop the gluten.
Digressing, in the days of my heedless youth, I used to imagine opening a store specializing in microbially-produced comestibles - bread, wine, cheese - and calling it Rotten Food.