http://bioinformare.blogspot.com.au/2016/02/survival-analysi... has graphs of survival rate over time broken down by manufacturer and model. Far more informative, you're right. I don't think Backblaze uses 6 year old drives. :-)
tldr; It clearly shows that HGST has an overall superior survival rate over time. WD is a distant second and Seagate in third (although the Seagate ST4000DM000 model is exceptional and fairs very well).