I didn't say they were, but look at the problems some of these resellers put up as soon as you try and return anything. Bitmain can't force external companies to do anything, so can't get involved with what is essentially a 3rd party dispute. If you purchase from a reseller, your contract and sale is with the reseller.
Yes, but we're not talking about the contract for sale, we're talking about the manufacturer's warranty.
If you buy an appliance at Walmart or Target or other retailer you usually can return a defective item to them for a cash refund but the manufacturer will often still provide a method to get a repair or replacement directly or through a service center. Appliance makers don't usually tell end-users to take a hike if it wasn't purchased directly from them.