Earlier quoted context omitted.
That seems like the weakest part of the argument — Walmart, Kroger, Walgreens, Costco, and every other major retailer has a similar program. All use sales data to determine what sells best and copy it. I did this for a decade, designing store brand medical devices for all the major retailers. There are plenty of legitimate critiques of Amazon. The "private label" one is by far the weakest.
Walmart, Kroger, Walgreens and Costco are not marketplaces, they're retailers, and they have contracts with suppliers and pay distributors to purchase goods to resell to consumers. Amazon is a marketplace where any retailer can list their goods for sale. I believe Warren's argument is that Amazon is abusing their position as the marketplace platform owner by listing their own goods at prices that undercut marketplace…
Whos books the capital sits on while its in a warehouse is absolutely the most arbitrary distinction in all of this. Amazon provides warehouse space, and the product provider takes the risk of unsold product. Its a fair trade that allows exposure companies wouldnt otherwise get, unless they convinced amazon to BUY their stock.
If anything is anti competitive, its walmart/apple etc forcing companies to drastically ramp up production, and then leaving them high and dry unless they accept low ball offers. It's exactly what Apple did to GT Advanced Technologies (forced a furnace company to turn into a manufacturing company, a deal they "couldnt refuse", and when they backed out / failed to deliver the company ended up ~90% smaller.)