The better analogy in this case would be to an AmazonBasics USB cable, not to a phone charger.

Are there issues when anyone can provide a product? Yes. But this would certainly not involve Amazon opening the storefront to allow selling any sort of drugs, but rather them sourcing generic product themselves and selling it as private label.

I would have no problems trusting this product to be genuine, just as I have no problems trusting their other private label products. It's a different sort of issue.