Some clarity on the Garmin Zumo XT and older GPX files.
In both cases below I am sending the GPX files to the Zumo XT via the Garmin Drive App.

If I send the GPX 1.0 to the Zumo XT it tells me I have too many “Stops” so I presume at this point it is seeng my waypoints as Via Points.
It then gives me another pop up with the option to convert them all to Shaping Points.
I accept the changes and the route is created in the Trip Planner perfectly.
The Track is also created perfectly with no straight lines.

If I send the GPX 1.1 (Not the Beta XT version) to the Zumo XT it automatically see’s all my waypoints as Shaping Points. (I never use Via Points.) and automatically creates the route in the Trip Planner and the Track is also perfect with no straight lines.