Every brick and mortar store has to assert the safety and legality of everything they sell or else risk serious liability.
From what I can tell, Amazon does not present itself as a farmer's or flea market, yet it tries to limit its liability by pretending it does. To the average consumer things purchased from it come "from amazon", as compared to ebay which makes it much more obvious you are purchasing from a particular person or shop.
Amazon really tries to have its cake and eat it too here, and it sort of blows my mind that consumer product safety regulators haven't clamped down on this.
It's really one thing to have basically anything available on ebay/aliexpress/others (consumer trust is much lower) and another to be a huge retailer (just like walmart) and yet to be able to sell whatever unsafe stuff you want (unlike walmart).