My takeaway... The specific model plays a huge role in the failure rate.
A great model has a MTBF of 250 years.
A bad model might have a MTBF of just 5 years.
I suspect if you had a need for reliable storage which couldn't be met with the usual RAID approach, buying 2nd hand drives from eBay of a model and batch proven to be really reliable is probably your best bet.
And to answer the obvious question... One usecase where you want reliability and can't use RAID is where you are selling a product that only has physical space or money for one drive - for example a standalone CCTV storage device.
Every drive failure will lead to an unhappy customer and product return, so you really want the failure rate in the first 10 years of operation to be 1% or below. (Which none of the drives in this study can do).
A great model has a MTBF of 250 years.
A bad model might have a MTBF of just 5 years.
I suspect if you had a need for reliable storage which couldn't be met with the usual RAID approach, buying 2nd hand drives from eBay of a model and batch proven to be really reliable is probably your best bet.