It does, behind private IP, your port might still be translated when passes through Maxis NAT. PS3 and the other end server in PS network will detect that as NAT type 3.

NAT type 3 - behind NAT and ports are blocked
NAT type 2 - behind NAT but port forwarding is done (applies to public IP, could be a problem with private WAN IP since you can't actually do port forwarding on Maxis NAT)
NAT type 1 - DMZ (with public IP of course)