I have been looking into this on my own and yes it has to be a proprietary bolt for any lever design to function.Curious what the bolt looks like, they have to have their own bolt right? Normal bolt travels back into the buffer tube quite a ways, this uses 870 stocks, no tube, so it has to be a proprietary bolt to work with the lever. They sure don't give much away in the video.
But the carrier has to be different, I can see them using the same bolt and cam pin but the carrier has to be different.It uses the standard AR bolt face.