I think there's a lot of misunderstanding, though, on what constitutes abuse (and thus an anecdote for your assertion). Amazon openly mines third party sales data to bolster its in house brands, just as Costco does with Kirkland, Walmart with Parent's Choice, Trader Joe's does with their house brand, etc..
Amazon has a policy, as described in this article, of not allowing individual seller's data to be used in non-aggregated form by internal parties. This is purportedly to make third parties feel less directly competed with, and is a guarantee not provided by my above examples (Trader Joe's, etc.).
There is not a mountain of evidence that they look at unaggregated data, and it is absolutely difficult to prove a negative on. For example, let's say there's a single brand breaking through in a new electronics category. Let's say some enterprising internal brand manager is looking for up and comers to pull into Amazon Basics. Why not just search the site for that type of electronic? Or look at short term best seller lists?
I'm on the fence about what should or shouldn't be legal in this situation. But if Amazon can't do it, it seems clear that Trader Joe's, Costo, etc. shouldn't be able to do it, and that's quite a can of potentially anti-consumer worms.
Amazon has the policy, and the journalists have found sources saying they break them, so at the very least an internal investigation is warranted, or some non-criminal external investigation for transparency's sake. But as far as I understand (I am so ready to be corrected), Amazon does not even need to have such a data aggregation policy, much less have an iron-tight way of policing it. What this really looks like to me is Amazon shifting from being a third party seller platform to a more highly curated internal/external hybrid platform, just as maker supermarkets did in the 90's. Believe me there was a lot of handwringing then about the practice at supermarkets, but now it is commonplace and one can argue that it is ultimately a benefit to the ecosystem.