I think the encryption must be an optional feature. I have two of the drives in 4 TB variants, but I'm not using encryption at all. They are just in RAID 1 and work as normal drives, though I suppose I could enable the encryption features if I wanted to (which I don't). I didn't do anything special in setting them up, so I think it might be worth giving it a shot.
But if you haven't opened the drive yet, you may want to return it for a 2.5 in drive with more storage. You'll be able to have it be internal that way.