A little googling using key phrases in that first link suggests that they've copied the description from this Western Digital drive. That doesn't mean those are the drives you are getting, it's more likely a "representative" description of what you'll get.

My other suggestion would be to take a look at /r/UnRAID - it's an OS that does its own version of RAID, that lets you mix and match drive sizes, and add drives without rebuilding the array. You might find that it suits your needs better than RAID-0.