Works for me on my XT through connector as long as I confirm the device (XT) is connected to Garmin Express. If the connection to Garmin Express isn't made then the export fails. I find that the XT can be tempremental in connecting to Garmin Express and sometimes takes a little while.
I transferred a route this morning (via connector) using both 1.1 and 1.2 Zumo file types - both worked fine.
I usually transfer the saved files from MyRouteapp to my phone though which has Garmin Drive installed and then transfer (as suggested by @nick-carthew) to XT is easier that way.
Confirm XT connected image -