The documents linked constantly refer to examining (as you would in a shop) - but not using.
It states you need exercise reasonable care whilst doing that. Considering the specs for the card were on the website and box; the card didn't even need to be opened, nevermind installed to know it wasn't going to work.
The DSR isn't designed to be a try before you buy regulation.
The supplier has done nothing wrong, the customer has made a mistake - despite all the information he needed being there. He's not fully understood what he's buying, used to the product and then gone 'oh ****'. By then turning to the retailer and shouting 'DSR!!!!!!!!1' you just end up looking stupid. If you want to cite the DSR, then cite the relevant parts of it.