It's because it's designed to be sold at retail, not on the off chance someone is buying it for a BTX case.
Ever seen an OEM card built for someone like Dell or HP? They are designed to be cheap (and look that way) because people buy them on specs alone and the cases don't even have a window.
The dual fan one is likely to be quieter but blows all the hot air into the case. The blower one is a reference model and better if your case has limited ventilation as it blows all the heat out of the case
Serial numbers are removed so you can't check to see if it is under the manufacturer's warranty. It's not, and is therefore only warranted by the seller.