They actually describe it as "6+1 degrees of freedom" [1] with the gripper being the "+1" - so it's got base, shoulder, elbow, wrist1, wrist2, wrist3, and gripper.

This is a conventional way of describing things. Traditionally robot arms come with a "tool flange" where you attach your own "end effector" (which might be a gripper, or a suction cup, or a welding gun, or a paint sprayer, or whatever) and we count the degrees of freedom before the tool flange separately from those after the tool flange.

Occasionally robots come with 7 degrees of freedom [2] which gives you more options for reaching the same tool flange position. This can be useful in certain applications, like working around obstacles in the environment. It's uncommon though.

[1] https://www.seeedstudio.com/reBot-Arm-B601-DM-Bundle.html [2] https://explicit-robotics.github.io/exp_robot/kuka_LBR_iiwa7...

I'm sorry, I was confused. This arm appear to have wrist pitch and yaw "backwards" from standard split forearm configuration, and I mistook the wrist yaw motor to be something else.

Although, it does still worry me that there don't seem to be a lot of footage of this arm with that axis away from its neutral position...

His point is that the robot has split the kinematics to have 3 DOF for position near the base and 3 orientation DOF on the wrist.

This still gives you 6 DOF on the end effector, which is pretty good, but overall the arm design is restricted in its ability to route around obstacles.

This downside has an upside though. Since every cartesian position has exactly one pose for the first 3 DOF, the inverse kinematics are simpler and you do not run into singularities for basic position control when maintaining a constant orientation.