[QUOTE=Immitis;20672060]thats not true, the achievement counts ALL mounts across the account except for class mounts and mounts that switch when you log onto a different faction toon (for example the silver covenant mounts, the gryphon/wyverms, most achievement mounts)
so for example say you have 150 mounts on an alliance toon then get 50 new mounts you dont have on your alliance toon yet you then get the achievement. According to the armory I have over 250 mounts, ingame it's around 180-190 (some mounts don't count for the other faction) for the achievment the number ingame will count.
The armory is bugged, it shows mounts of both factions. You can't have them at the same time as they get transfered into the specific faction equivalent when logging on a Alliance/Horde character.