Lawyerboy: you're not a slow learner. Flying is taught (and learned) in layers of complexity - as one layer is mastered another layer is added.
It is not unusual in this situation for the student to have difficult with the next layer, as the previous layer will have only just been mastered before the instructor pushes on. If the next layer is particularly complex (and other posts have indicated the vast number of activities involved in cross-country navigation, so I think we can take it as read that it is!), taking some load of the student is bound to be helpful. Sounds like you have had a good instructor.