Amazon is a retailer, they can choose to sell or not sell whomever’s goods they want to.

Amazon is also platform operator. This is about Amazon being the direct seller on the selling platform operated by this company called Amazon vs third party seller selling Apple products on the platform operated by this company called Amazon.

Meaning stuff like Amazon placing their own direct sell offer higher on results or as said how prominently they featured advertising by their party sellers.

This is the danger of trying to operate both as the retailer and as the platform operator on same market place. Competition authority will very carefully scrutinise ones operating of the market platform on benefit of ones retail sales.

Direct single party retail webshops don't have this problem. Neither do pure marketplace platform, where they just run the marketplace and don't offer any first party product sales.

They could choose to not do third party sellers and be pure first party retailer. However then their selection would be smaller. Since third party sellers cover much of the niches not lucrative enough for amazon itself to cover. Then Amazon wouldn't be the "buy everything" store, which would also hurt their retail business. Since the default move wouldn't be "well lets first look on amazon, they have everything there".

Amazon is trying to have their cake and eat it too. Competition authority is saying "hold on there now, you either eat it or keep it. No cheating and double dipping." If you are to be both market place and retailer, there needs to be firewall between those two divisions and fair dealing with the other retailers on your marketplace.