This is the new design by Power Planter for commercial use. One of the challenges with the other (non THD) models is that the hex end that goes into the drill can get damaged if the operator hasnt tightened the chuck well on the drill. It ends up spinning in the chuck and stripping the head. Once stripped the whole Power Planter needs to be replaced.
The solution was to make that end piece replaceable by changing the design around.
NOTE: We don't generally recommend this size Power Planter for home garden use. This is a professional grade auger used by Landscapers and does require a higher spec drill and previous knowledge with power tools. It is NOT suitable for cultivating the garden, but is great for digging post holes. For DIY home garden Power Planters, please see the Home Gardener Range at this link.