That link looks like it’s from the previous generation hardware. The Omnia is similar.
You can see the current switch configuration in LuCI under Network > Switch.
The default configuration is: ports: LAN0, LAN1, LAN2, LAN3, CPU(eth0) are in one vlan
and LAN4, CPU(eth2) are in another vlan.
By default, traffic to/from LAN4 to/from the other LAN ports go through software switching (the Linux bridge br-lan).