Anecdote time. Last year I bought an Anker power brick via Amazon, using the link on Anker's own website. When it arrived, instead of Anker's normal well-designed retail packaging, the brick was simply wrapped in bubble wrap, with a printed label stating that it was "new" and thrown into its shipping box. I inquired with Anker support about this, but they could only say that all their products they send to Amazon for distribution are in retail packaging. I did confirm that the item was purchased through the AnkerDirect seller, so I can only guess that it was either a returned item or that the retail packaging had been damaged, and someone at the Amazon warehouse repackaged it and put it back in the "new" bin. I ended up returning it for a refund. My trust of Amazon as a retail platform has been steadily eroding over the past few years, and this was just another reason to shop elsewhere.
The thing is, the commingled stickerless inventory program is only supposed to apply to items sold by Amazon, not to third parties like AnkerDirect, so the hypothesis it's fulfilled-by-Amazon that screwed the pooch is more likely.
That would cut down on the number of shitty dangerous power suppliers they're selling.
Certifications from UL or similar labs are much better, but many producers don't hesitate to also fake the UL logo on their fake products.