Everything bought from Amazon, including from Amazon Marketplace, is covered by the same policy. The individual vendors have no say about it. It's enforced by Amazon. Since Amazon is the payment processor, if worse comes to worse, Amazon will simply not pay the vendor and refund the customer.
Amazon.com Help: A-to-z Guarantee Protection
Beware though, everytime you have a customer service action. Be that a return or a price adjustment, Amazon will note that in your file. Do it enough times and you will be banned from Amazon for life. So only return when you really need to. Amazon is not a good vendor to use for people that like to buy and try.