It's a route brought in from Basecamp, eventually - the XT will still only occasionally connect to Basecamp on my Mac even with Express closed. I tried exporting and uploading via Garmin Explore but some of the shaping points did not transfer, so I copied the exported gpx to the unit and this is what it previews through route planner, which is the only way to get it to follow a route as far as I can see.
The route is only small, about 120 miles so not exactly pushing it. You can view it (temporarily here:
https://www.gpsvisualizer.com/display/20210810025638-67156-map.html
There are no avoidances or preferences that I can see which will make it turn off a tarmac road and go down a single track, turn around and come back out?
This is a future trip so I have the luxury of reviewing it and now knowing that I don't make that turn, especially with 6 people following me
In a Rally scenario you've got to trust it the unit bit more, something I'm finding hard to do