Thanks for the precisions @LA Guy
That's what I had in mind for the indigo dye.
If it were a black poplin bag for instance, it would be unlikely to have some color bleeding (at least not in the same proportions as with raw denim).
What makes it different here is because it's a denim textile, and as such the dye can either be "regular" (same as the one used on t-shirt, sweatshirt, cotton trousers, etc..) or "jeans" specific (which means possible bleeding). Is this...