Yeah, about that. PvP has some mount rewards, sure, but look at this latest official census.
http://livedoor.blogimg.jp/tekitou_m...b/eba2e16d.jpg
Out of 70+ mounts in the game Mentor mount is the rarest because it's new and hidden by insane grind. But the rest of rarest are PvP mounts.
Such a little amount of people play PvP that anything related to it is already ultra rare, only a few players per server have these mounts.
It's already exclusive to pvp regulars without any time limit to get them, no need to make it even more rare by timegates.
Not to mention they rarely if ever use these mounts because they don't participate in any PvE activity, they don't appear in overworld areas, I see them only afking in Limsa waiting for the next pop
all the time.
Designing mounts for PvP regulars is only a waste of developer resources.