My understanding is they got caught with this in the mid 2010s and as a result had to come very clean on some of this inter-departmental stuff. Most people who've worked at/with Amazon know its fief-like bureaucracy and clean delineation of business units (as both a strength and a weakness), so I'd be curious if there was more to it.
Then the other question would be: if you run a system that has certain emergent behaviors coming from it, without direct collusion -- how much would you be on the hook for various things that do end up happening? It makes sense that Amazon search wants lowest prices on Amazon, and it makes sense that Amazon VC wants margin, so when the two effects result in price inflation is that Amazon's problem.
IANAL