I'm using mapster and really like this feature, but I'm not sure if it's supported. I installed the addon today and the only areas I visited were TB Peninsula and Twilight Highlands, and in TBP, everything was visible, but in TH, everything was 'undiscovered'.
Also, upon unchecking the box, everything becomes invisible (undiscovered and blank) on the minimap. I didn't take a picture of that. To fix this I had to reloadUI without the addon.