I have just tested Relay feature myself and everything worked as expected. Detailed steps:
- Connected to a WiFi source as a client.
- Checked if I can access the internet from router CLI (ping google.com)
- Navigated Network > Interfaces > LAN
- Disabled DHCP and Enabled Relay. Also selected WWAN interface below enable slider. Save and Apply.
WWAN interface was up as before and my PC connected via LAN cable obtained IP from wireless interface.
I would suggest double-checking your steps, also you are using an older firmware version (update to RUTX_R_00.02.06), check if WiFi source is reliable and connected to the RUTX10 before relay configuration.
Also, that documentation is not outdated. It is an example on how to enable Relay feature in RUT9 devices.