No, not entirely. I think Amazon cares about commissions. They want the marketplace to keep pumping out money for them and they want to paint a nice rosy picture of things so that it looks safe and legit. To that end, they don't give a shit what their vendors do as long as it makes them money. If you get screwed you'll get taken care of, they still take care of customers. But they take care of customers on the squeaky wheel principle. Have a problem, buy a counterfeit item, notice, complain, get it fixed. But nothing more than that. Amazon won't do anything proactively to protect other customers. The company that tried to rip you off you can go on selling counterfeit items to other customers and generating fees for Amazon. The ones who notice get a refund, the ones who don't get screwed. And with most counterfeit items, most people don't notice. So like 5-10% notice, file a complaint, get a refund. 90-95% keep the counterfeit item without noticing, Amazon keeps the commission and they're happy. They know that the company is selling bogus merchandise, but their intervention only extends to refunds, not to getting rid of the bad vendors.
And yes, personal experience. Amazon goes to great lengths to sweep problems under the rug and to allow shady 3rd party sellers to continue to run scams. They fix the individual complaints only and don't do jack about the source of the complaints.