It needs to gimbal in all directions, the weight of the auger means it always will hang level. Unless you're only going to do holes from a direction where you're level side to side, that is. For me I wanted this so I could get to holes that only had very limited access, and even the level parts of my yard aren't level, so most of the holes were fairly off camber. Yes, the holes won't come out perfect, as the bucket never goes down directly straight.
If you look at the skid steer auger attachments, they use a universal to gimbal as well, but they don't source their universals from old driveshafts. They operate in the same way, the weight of the auger just makes them hang level, however they are a little more forgiving as it's easier to see what's going on, and you can fine adjust the position of them easier. They're also $4000 new, and a proper used skid steer is twice the price of a used B7100D, you get what you pay for.
