"It is the system you "refer" to when comparing it to others."
@boxcarman - Bingo! It is as simple as that.
The connotation has been misapplied to products by manufacturers and others to imply what might more accurately be described as a "signature," "flagship," or "premier" product. In the case of audio systems, a "reference" might be more closely aligned with a "benchmark" (not the company) in that it is something to compare to, but should not be mistaken as SOTA, which itself is not a fixed point, similar to wine, art, and other things that are subjectively judged.