Are you worried about the QD swivels being free to rotate endlessly, tangling up your sling?
The way I understood the description, it lacks the ability to lock your swivels at 90 degrees, but the location of the adapter in proximity to the side storage tubes allows the swivel to rotate freely only in a limited range. (Lets say 120 degrees in each direction.)
This would prevent your sling from twisting so much it would get tangled.