A friend has a 2011 Keystone Cougar that he is living in full time. The RV is wired for two TV's. The living room has the booster/12vdc plug and next to that is another wall plate with two coax plug...
My Jayco has the same thing. It is how you connect the other tv jack in the bedroom and switch between cable and antenna and cable and satellite . It is a poor design and confusing I had to make a cheat sheet and keep it in tv cabinet. After 3 1/2 years I think i figured it out now.