In garmin mode, when you hook to a pc/mac it will ask if you want to be in mtp/mass store mode. If no, you,can't copy things to/from the watch, but it will charge and continue to run apps/etc So the same if you hook to something like a wall adapter of a external battery pack.
So essentially, the only reason someone would want to use Garmin mode is if they want to charge it from a computer and still be able to use the watch as normal?
