I’m leaning towards your idea Jojo, because while the right ear has a long enough bolt that accommodates the strap and an additional washer and nut, the right ear screws in the opposite direction into the earpiece and with a shorter screw.
The MCR and RS helmets appear to use similar hardware which I understand is accurate to some degree, and the top left screw is not long enough to fit through a strap. I came to the same conclusion as you did, though I’m not sure if it’s nylon or metal, and I think the nut might be square?