I can see hiding reserve, ( show 1000 with 9000 behind), but what's the point of not exposing your price?
IMO hidden orders are mostly used to hide true size.
Ex. For a sell order, show 100 @ 43.90, but have 900 more @ 43.90 or less hidden.
Hidden orders are also used in very liquid stocks as a way to cut in front of another order without their knowing it. This would be done to prevent others from then cutting in front of their order. Anyone who's ever traded QQQ thru ISLD has more than likely been filled at a weird price like 29.096 when the best displayed offer was 29.10
I'll double check Monday.