flaps on respironics dream wear full face

I just received this mask, Respironics Dreamwear full face, and I'm confused by the silicon flaps that cover the large vent holes. They open when I inhale and close to block the holes when I exhale. That means that when I exhale, only the small vent holes are open, and I'm exhaling directly into the incoming air pressure from the machine. This doesn't make sense. With my nasal mask there was plenty of venting. I could put it on and air would be rushing out the holes both while inhaling and exhaling. On the full face, air goes out the main holes only while inhaling. During exhale the main holes are blocked and only some tiny holes are open. Is this the way this mask is supposed to work??

What you are describing is the anti asphyxiation valve. It works this way when no air is flowing from the machine. Once you start the machine, the valve will stay in the open position allowing air to flow to the mask. If your machine quits working, the valve allows fresh air to enter the mask and forces the exhaled air to be expelled from the mask.

The anti-asphyxia valve stays open if there is a power outage.
Preventing asphyxiation.
Nasal masks/pillows don't need it, because you can/will breathe through your mouth.