Flat towing a 2017 Ford Fusion 2.7L, AWD w/auto trans.

And then it says 2.7L awd can be.......

2017 Fusion Owners Manual Pg 226:

All-wheel Drive Vehicles
All-wheel drive vehicles CANNOT be flat-towed (all wheels on the ground) as vehicle or transmission damage may occur. It is recommended to tow your vehicle with . all four (4) wheels off the ground such as when using a car-hauling trailer. Otherwise, you cannot recreational tow your vehicle.

So, I read both of your posts asking basically the same question about two different vehicles, and the answer is it doesn't matter what vehicle is being considered, any "brake in a box" that uses battery power from the towed vehicle will deplete that vehicle's battery. The solutions are a) run a charge line from motorhome to toad to keep the toad battery up, b) use a "battery box" (a portable battery booster with it's own battery). Some members on here have reported success going this route. c) Get a braking system that doesn't need power.