Hi,
Traffic from your openvpn server to your other hosts on the network do not pass your pfsense appliance since the vpn server has an direct route to the "internal" network.
However, traffic originated from your hosts on the network towards the openvpn client subnet, routes via your pfsense appliance, since the hosts on the internal network does not have a specific route to the openvpn client subnet. Therefore traffic arrives and goes out on the LAN interfaces of your pfsense box. I think you need a rule for that, or enable the option you mention. I have no experience with this kind of setup, but you need a rule like this I think:
allow source <lan ip="" range="">destination <lan ip="" range="">on the LAN interface.
The other approach is to add a static route on the LAN hosts, but is more work and harder to maintain. To test you can manual add a route on a LAN host.
Also, only the first packet of any traffic will be directed through your pfsense box. Most operating systems has an "ICMP redirect" implementation, which you might have to enable. This way the host on the LAN network will learn the direct route to the openvpn clients through the openvpn server, bypassing the pfsense box.
I Hope this will help you.</lan></lan>