Thank you Seerah. I need to test, but I'm beginning to suspect that isContinent will be true if the currently viewed map has quest objectives. Unless you had zero quests in your log, or zero for a different zone, it will always be true for the greater map view.
For example, those of us leveling in Warlords would return true for Draenor, but what I was seeing at the time was that I had no quest objectives in my Garrison. However, I do have some now, and I certainly have some in various Draenor zones, so I'll test those.
Zoom out to the cosmic map, and it will be true, because Draenor as a whole fits into the cosmic map.
I think you've put me on the right path.