N80, you stated that you are new to the audiophile world. So, shouldn't you approach the subject of burn-in or run-in with an open mind?
The instructions on your cables to allow 175 hours breakin does sound absurd and I've never seen that before. You may have purchased Mogami or Canare from that particular dealer which are professional quality cables.
I work in the biz and use these cables and break-in has never been mentioned.
But based on my experience at home with cables using exotic metallurgy and design, there is an audible difference between the brand of cable plus the before and after breakin period. ie, I have owned 2 pairs of Purist Audio interconnects and could hear a difference between a new cable out of the box and the cable in my system.
At some point in this hobby you may discover this for yourself.