Hi mate, yes the ESC doesn’t fully switch off even when the TC is turned off, this for me is only a problem when doing short sharp turn when the front end push out to much (under steer) because of my heave foot, it takes a bit of time to get used to how to make short / drifting turns with it though but its not a problem for me when driving “normally”, its only an issue when starting “playing” around and the back end doesn’t step out / break traction.
I've never had issues at speed or while side slopping, fast drifts and most doughnuts
My truck is a single cab though so I'm sure getting the longer double cab truck through the dunes might be more of a challenge as you have much more weight and length to deal with especially when turning...
Also I've no idea how to deactivate the ESC so maybe something you’ll need to ask Ford technician about...
Do let me know when you find out how to turn it fully off, I’ll also try and find out and post it here when I do✌🏼