Thanks for the feedback! This is indeed odd behavior.
Mounts that look good on the ground (those that don’t hover) are preferred in non-flying areas. It sounds like some of the areas you describe don’t work as expected.
Interestingly, I don’t think the opposite is true, but it sounds like it would be preferred (e.g. if you are in a flying area, only flying mounts are summoned, assuming at least one of them exists in your favorites list).
Let me know if I got that wrong.