I hadn’t ever really heard of it until now, but I found out that 2 or the rings attached to the cheek pieces and the other 2 are attached to the reins. The article said it was for driving though... it said that it is a bit that you can turn easily in (as is would stay in place better) so maybe that’s why people are using them? Hope this helps!
The Dutch Elevator bit? It uses leverage on the horses mouth to elevate the head.