Maybe he meant as a primary heat source. Obviously it's a fire....indoors....that generates heat.....so a secondary heat source - sure! But given the restricted time intervals of running them and the precautions to heed to, it should not be used as a primary heating source?
How do these ventless fireplaces stack up against the 5 brick wall heaters in terms of safety provisions? My parents still have a 5 brick Vanguard wall heater in their house for back up heat in case the central unit fails. Never really thought of the comparison between the two, because both are burning natural gas/propane in an unvented fashion.