Fixed tow ball and rear sensors

 I suspect you are right but as I am partxing for a new Sorento I dont really care. On the subject of reversing sensors, as long as the fitter uses a VSK  ( Vehicle Specific Kit ) then hitching up and connecting the electrics will automatically close down the rear sensors. VSK's also relay any problems, ie blown bulbs, and display on the dash. I have also learned recently that many main dealers actually bring in outside fitters for tow bars and electrics so dont assume that a tow bar fitted by a main dealer is done by there own staff. 

My Honda CR-V has a fixed towbar and never had a problem.  My wife’s car has a detachable and whenever it’s fitted and reversing the sensors activate continually.

Whilst I have a detachable towbar on my Hyundai Santa Fe, I do leave it attached for long periods of time, even when not towing. The sensors do not detect it at all.

We've a detachable one on our Volvo and have had no problems with the sensors when it's attached.

Fixed towbar on Mondeo with no problems. When reversing you are OK until the bleep is continuous! If you stop immediately at that point you have about six inches clearance on the ball .

Fixed tow ball on  a Kuga sensors work fine.

I had reversing sensors fitted and they are wired so that they are only active when reverse gear is selected. On the occasions that I reverse the caravan up to the peg, I only have to listen to the beeping for about one minute as I usually engage the motor mover to line up the alko wheel lock. 

all sensors only work when reverse is selected as if not when vehicles behind you at lights get to close they would be bleeping away every time. I have button on dash that turns sensors off when towing as not required and I can put towball perfect under tow hitch using reversing camera.