It's been some time since you've posted this, how'd you fare with your '15 Edge if you got one?
Here's our story:
We just traded in our '17 CR-V for a '15 Edge and have found the same information. Our Ford dealership was just as clueless as the Ford documentation. When I called the main Ford 800 line for technical support they just referred me back to the dealership. So, just yesterday we finally picked up our Edge and towed it home behind the coach and all went well but I am not taking chances and am going to remove the negative cable when we tow which is quite a hassle. I have found what appears to be a great manual cutoff switch on Amazon. When we get back from a short trip next week I'll be ordering it.
All in all we love our new-to-us Edge even though it's missing a couple of bells and whistles the CR-V had. It's peppier and has a whole lot more room overall and it's only a couple hundred pounds more than the CR-V/dolly combo coming in at just around 4,000 lbs. and it tows four down like a dream.