It wouldn't be the first time that a reseller or even Humax themselves have got it wrong. Actually, thinking about it, Humax are most likely.
It's largely irrelevant though!
Following on from the comment about the earth strap, I've noticed a variation in how the SATA cable is routed and secured (or not) to the drive caddy. There's a slot in the plastic at the top that I've seen the cable pushed into (looks designed for it) and I've also seen a wire wrap held on one of the caddy screws. I don't know if methods evolved or if they were just built at different places.