confused about wording

[ppbrro]

now at the end of the description of the achievements "obtain X mounts" it says "usable by a single character" what does it mean?
did it change the way it count the mounts somehow?
maybe what i am asking is stupid af but i don't understand

[Mascotte]

Nothing changed.
Its just that certain mounts don't count (they never did) for the collect x amount achievements.
People often tried to roll opposing faction deathknights to greatly increase their 'mount collected' figure since each race has a ton.
That never worked or counted, the achievements just got updated to be clearer on that front.