Amazon used to retail tons of products, for two reasons:
1. Comparative ROI of different business models at different scales. When you're smaller, there's more money in being the middleman (if you can source products more cheaply through negotiation or clever sourcing, you can capture a large profit margin); and there's less money in being a logistics provider (since, without a built-up brand in the space, you have to compete on price.) Now that Amazon is huge, the scales are flipped: being the middleman and sourcing products is now more of a burden than a profit source, while running a well-known and trusted logistics provider is now a huge profit center. But this wasn't always true.
2. Bootstrapping. Consignment is a partnership built on trust. Big manufacturers won't do it with small/unknown storefronts. A retail supply-chain relationship (where the goods are—from the manufacturer's perspective—a sale, as soon as the retailer takes possession of them) is safer and lower-commitment for both parties. It's like hiring someone as a contractor instead of as an employee. Amazon ca. 1994 needed goods in their storefront, and the only way to get those goods into their storefront as a relative unknown was by buying them at wholesale, like a regular retailer.
> So, just to check my understanding, this move by Amazon won't really affect anything as far as I am concerned as a customer?
Definitely; in the long term, nothing will change. But, in the very short term, you might see a blip.
If nobody other than Amazon was selling some product on the Amazon storefront, and the manufacturer is asleep on their feet, the product's listing might pop out of existence for a few days, before the manufacturer bothers to take possession of the listing. Every manufacturer that Amazon was retailing for inevitably will re-list the products themselves (as a consigner), because Amazon is now too large to ignore as a sales channel.