The problem with this is that if a non-manufacturer sells the "same" product, and they both use the same warehouse, Amazon keeps both versions of the product in the same bin, and there's no way to guarantee whether you're getting the real product or the knockoff.

If you buy post-it notes from the official post-it's Amazon store, they're not necessarily giving you post-its from the official post-its stock. You could be getting post-its from seller A6Zodiyn which were never stored properly and several years old so the sticky note glue doesn't hold anymore. But both sellers were selling post-its in the same packaging, so they're in the same box in the warehouse and what the pickers grab is random.

But also the completely fake post-its are in that box too, and they don't stick as well plus their color is off, and there are fewer sheets per pad. But because the outer packaging is the same, same same warehouse box.