My car has the "flat" towing electrics connector and I bought a couple of "adapters" at the Perth 4WD show (flat to round etc on a short piece of wire). The plug is the OEM one connected to the hidden plug and I just use the appropriate adapter to connect to what ever the trailer is fitted with.
I've towed all sorts of hired and borrowed trailers (don't own one myself) as well as a couple friend's boat trailers over the past couple years with all sorts of electrics and lights (LED and other) without any hassle.
Sounds a bit like salesman "storm in a tea cup" issues...
Cheers,
Lou

