Sorry to awaken this old thread again, but my question is related.
I have a Fenix 5 Plus, but it is a general thing: Why is it necessary that my device is connected to garmin express to download the maps? To me, it would make much more sense to download the maps in advance and once they are on the computer, I connect the device and install them. A several GB maps update for sure will take some time to download, and it will take some time to get to the device via USB, but much less (assuming 30MB/s USB 2.0 speed this is still 20x faster than my current internet speed). The two processes should be decoupled.