Occasionally, a hunter will have sneak and hide engaged such that you can't see the hunter, but the mount will be following along perfectly visible. This might make sense in some hunting scenarios (crawling through the grasses, communicating with your mount through clicks and giggles), but I do remember being confused by this inside the city as a new player:
A war beetle sneaks west.
Just suppose you couldn't see its owner in all the traffic.
And yes, supposedly some mounts also sneak and hide according to their description. I'm not entirely sure if this is codedly accurate though as I haven't found a way of testing it. We need a giant mirror.