"Network Error" popup message when trying to create courses on trails in remote settings (no WiFi or cell available)

While hiking in a remote wilderness location, I had no success creating courses that followed trails.  Prior to the trip when I still had internet connectivity, I was able to create courses that followed these same trails so I know that the Explore topoactive map recognized the existence of the trails of interest.  However, I could not create a course once I was out in the woods, even when I tried to duplicate the exact same course I had made previously. 

What happened is that I was able to enter the first point, but when I then attempted to add the 2nd point, the app drew a straight purple line between the 2 points (didn't follow the trail) and a red popup message appeared saying "Route could not be calculated.  A network error occurred."  (I'll try to attach an screenshot image to make this clearer).  Interestingly, once back at home, I find that I get the same behavior and same message if I try to create a course with my iPhone in airplane mode.

Can Explore only create courses when it has connectivity?  If so, I don't get it because the ability to make courses in the field is an important feature.  Or is there perhaps some setting I'm overlooking that would circumvent the network error/direct line issue?