I have yet to see a first stage where the seat rests on the orifice when the reg is depressurized.
I have not either. All my regs are designed so the seat rests off the orifice w/o pressure. I think I recall some first stages using a normally closed HP seat, but I may be mistaken. Not servicing a large range of regs I mostly know about my own.
It makes sense as well as if the orifice rested on the seat in any first stage design, absolutely nothing would happen when you turned on the tank valve.
Just because a reg is normally closed, however does not mean it will not open when pressure is applied. Thinking it through, you may have problems balancing it though.
Of those that don't, balanced regs will experience less set over time as the spring pressure is much lighter in the balanced design.
Much lighter, but only when the reg is depressurized, right? I never really though of this. That may be the first real advantage I've ever heard of for using a balanced second stage.
Tom