As the title suggests, the article merely allows SEP clients to use the SEPM as a proxy server (this is not a reverse proxy and is clearly mis-titled) to get out to liveupdate.symantecliveupdate.com.
If the SEPM has no internet access, then it's not going to help you.
You'd be better off looking at a LUA and following the below:
http://www.symantec.com/docs/TECH106254
At least this way, you can point both RHEL endpoints and the SEPM at the internal LUA, and just update the LUA everyday.