No fuel spray or air spray when relieving fuel system pressure

What is your question?

I start with the gas cap, and it definitely lets out a lot of air pressure. But when I go to unbolt the service bolt to relieve pressure, nothing comes out. Fuel or air. And the manual says to be ready for spray. So I'm just wondering - does that mean my fuel pressure is not accurate? Or is removing the gas cap doing the job mostly? Thanks