The cynical perspective is that they are facing a serious financial penalty either from the manufacturers themselves, or a large buyer that got burned by co-mingled products, or both.
While high value resale brands like Apple and GPU manufacturers would be the obvious choice here, I’d be tickled if it was LEGO Group that finally forced their hand, given how many stories there are of people receiving faked parts, missing mini figs and straight up bags of pasta.
That’s not cynical, that’s the system working. And if you keep bringing your money, you are signaling it’s a little annoying but not it’s ultimately ok.
I can't count the number of times I've ordered a book from Amazon (1st party, Amazon as the seller) and received an obvious counterfeit, with fuzzy text and a poorly printed cover. On one occasion, the scanning/OCR process had missed most of one chapter, so there were just section headers, page numbers and blank pages.
Unfortunately publishers and manufacturers don't have a lot of leverage with Amazon. If there's pressure coming from somewhere, it must be coming from a regulatory body.
The best we can hope for is a world where Amazon faces real financial pressure to prevent counterfeits. Thus far I haven’t seen much evidence this was happening, but this is a welcome sign.