GoGoMount always summons a flying mount in an area you can fly, regardless of what mounts you have chosen. It also summons water mounts if you are in water, like the turtle or squid or stingray. You have to check off mounts in the addon's list though, it doesn't use your favorite mounts.
Edit: I just noticed you want flying mounts in nofly zones. GoGoMount does have an option for that as well, so it randomized all your selected mounts in ground areas.