While they don't delist items, their algo favors products they sell directly to the extent that Amazon will get the buy box over a third party seller even when that seller is reputable and cheaper. Add that the 3rd party seller has to pay a sales fee to Amazon, often making it impossible to compete with them without approaching zero margin.
It's not delisting but it's the next best thing. If Amazon starts selling something you sell, your sales are gone, you were just free market research for them.