I have always struggled with the logic, and perceived benefit, of such systems. The explicit base assumption of such systems is that the motor/controller simply cannot provide the torque required to do the job correctly, which means the system was poorly designed from the start. "Closed loop steppers" seem a crazy expensive and complex solution to poor design. For less money, you could design the system properly, and never have to worry about losing position. For about the same money, you could build a servo system, and likely get better overall performance.
And, note that, even in the video, the motors do NOT maintain position. When the guy grabs the wheels and turns, the motors move. The only thing that's different is that AFTER he lets go, they return to where they should have been all along. How is that "unstallable"??
Regards,
Ray L.