I agree. Not sure how much experience you have with 3d printed gearboxes, but they tend to be very noisy. Even at light loads. In contrast this is extremely quiet.
Like you I doubt it's useful for much work, but I found it interesting. Who knows, maybe useful for high rpm and low torque applications where noise is an issue.
True. I would think though that direct electric drive would be better for that though. You don't really need gearing if you can attach a motor that achieves the right target anyway, and those can often be quite small. Like if you were trying to drive a fan (the high speed low torque application that comes to mind), it's almost certainly easier to hook it up the the motor.
It kind of reminds me of this: https://www.youtube.com/watch?v=uD7Lzv5fWhs
(post is archived)