Mr. Heater Gas Valve Problem

I found this is this correct instructions?

http://www.allpartsinc.com/media/attachments/products/18672REVD.pdf

You want to be absolutely sure the wall stat is rated for "millivolt" systems. I have a living room corner heater. When it was installed I used no14 "Romex" as a stat wire because I wanted NO problems with voltage drop.

Don't get me wrong. Before the advent of 12V electronic ignition (in RVs) there were SKILLIONS of millivolt/ self powered systems in use. MANY MANY small houses and apartments that did not have central heat had some form of self powered gas heater Ever seen the tall "wall" heaters? or the more modern wall mount boxy heaters? Or the "corner fireplace" ones? ALL these are self powered systems