MAC Limitation?

I appears that the MAC doesn't allow separate networking to two different interfaces (public and private, for example) through two different interfaces (wireless and wired, for example)... even if the routing table reflects the correct routes (netstat). Has anyone done this before?

Yup, I've done that.
Airport using DHCP, and ethernet using manual IP address (not in the same subnet).

The Airport provides the wireless router capabilities. However, lets say that you want to use the wireless for all your public (web/email) traffic. Then, connect the Enet to your private network (10.0.0.0, for example). The MAC installs both routes as the default. Even if I remove the Enet default route, the MAC does not allow traffic to route to the wireless. IOW, the all traffic (whether configured on the route table or not) prefers the Enet. Very Strange.