That’s somewhat different. They aren’t taking stale bread and reusing it to make new bread, but rather a portion of the raw dough from a previous batch is saved and added to fresh dough. It’s meant to add a bit of fermented flavor, without quite being a sourdough. It’s more in line with preferments like poolish and biga.
Its a real thing, there’s a term for it if i can find it.
Edit; Pate Fermentee, or “old dough”, setting aside a hunk of dough from todays batch to mix into tomorrows for extra flavor
Theres also a method called a “soaker”, using stale bread in water, breaking it down, and remixing it into a new dough
That’s somewhat different. They aren’t taking stale bread and reusing it to make new bread, but rather a portion of the raw dough from a previous batch is saved and added to fresh dough. It’s meant to add a bit of fermented flavor, without quite being a sourdough. It’s more in line with preferments like poolish and biga.