The geometric forces not being likely very even and possibly even binding in various points of the travel causing uneven wear and tear on the mag tube and fore stock.
I wouldn't expect this thing to be fired enough for uneven wear to become an issue.
It looks more like the foreend has rails on the bottom and sides and this loop just bolts on to the bottom rail, so it could be added to most anything with a rail in the appropriate spot.
But yeah, that thing is nuts. And not in a good way.