It is an indirect or a fancy way of saying individual has assembled one or more other audio systems in the house, but this specific one is the "reference' because it is sounds "better" than other system(s). This "reference" system in all likelihood has a dedicated listening space/room whereas other systems may be in the office, bedroom, work area/garage, home theater setup, etc.
I have two systems, one dedicated for audio only and the other for both audio and video. I don't call any one of my setups reference because that's all I got (LOL).