@Con-Hennekens Thanks. That lead me to dig a little deeper. The ride in question was created by the ride coordinator using Kurviger, then he distributed a gpx 1.1 file created by Kurviger.
This gpx file does contain time values for each gps point in the track, no doubt that coincide with the calculations the Kurviger made for the route. That's why the route in Kurviger and the track's times coincide, and why the Garmin MyMap time, the MRA track time from the imported Kurviger track file, and the MRA route-track time created from the MRA track that was imported from the Kurviger track all have exactly the same time.
When Kurviger creates a gpx 1.1 track time it includes the time values for each gps point. When MRA creates one it does not (I double checked). However MRA, and Google MyMaps do read and use these values during import. Interesting. I've included screenshots below of the beginning and end of the 1.1 gpx file for the route that I'm talking about.
Bottom line is for this particular route Kurviger's time calculation was FAR more accurate than MRA's, especially when using the HERE map. I would think that would be worth looking into, but it's probably a low priority.

