According to TID 3988333 the description of this parameter is "Default behaviour is to send an SSL authentication redirect to a host name instead of a IP address. 0 to disable the same. Requires PXY023 or later."

Also, the default setting in Proxy.nlm is 1. However, in Craig's Proxy.cfg he has it set to 0. I would think you would want this to be set to 1, no?