Yes, because Bestbuy is the seller here, I find absolving Bestbuy of any blame here weird.
Or to use an analogy this would be like a car dealer refusing to fix a car because they're technically not the car manufacturer.
Part of th franchise agreement that dealerships contract with the manufacturer is that they will take honor warranty repairs. If you buy a Honda that someone traded in for a f150 at a Ford dealership the Ford dealership doesn't honor the warranty. The warranty is transferred from owner to owner and Honda still takes over warranty repairs.
Of you look at these listings on Best Buys website, it's not like they are buying these things off the shelf in the store with no information that they are facilitating a sale from a third party. Ebay does this all the time and no one cares, if you want a warranty from Amazon on things like this they try to sell you one before you check out or you're on your own. Infact, Best Buy sells third party warranties for products like this sold on their website and if you don't buy their warranty, you're stuck with the third party seller. This isn't some new thing that people haven't figured out yet. there is a a big difference of buying something from best buy and buying something through Best buy and it's not like they try to hide the difference.
The standard practice in these incidents is to either get your stuff back and handle the warranty through the seller or the retailer offers you a refund and you return the product. The the retailer goes after the seller. This person more than likely choose to have their product returned.
This isn't a bait and switch, best buy isn't trying to steal anything or get out of paying for things. Whether it's Amazon, newegg, best buy, eBay or even Walmart, the warranty and responsibility is through the third party.
If this was a stock laptop with OEM parts then best buy probably would have ate the cost and fixed it, but that's not what happened. They opened it up and found that the parts that need warrantied aren't even OEM parts. At that people the "we'll be nice and fix it anyway" thing goes out the window. Goto best buys website and try to buy something from a third party and goto check, look at all the warnings and notices they make you go through before they let you hit buy. They aren't things hidden in walls of text like a license agreement, they're a few sentences long in bold, highlighted text.