Wrong
That website isn't all that accurate.
Here's mine:
I went through my collection wondering how the numbers weren't lined up.
Apparently some mounts are bugged on the website, like the DK's Acherus mount and Brown Horse, they need to be added to your collection manually. (not added before picture)
There's even more bugged ones on horde (Chauffeured Mechano-Hog and Swift Warstrider).
The Vash'jir Seahorse is NOT account wide, you have to complete the quest per toon.
So, check it and add them, they will line up.
You can check each character's mount total by going to Achievement > Statistics > Character > Gear. That will show you the number that that toon can mount regardless if they have the profession.
I'm at 295 towards the achievement, I would've been at 297 if I put my Vicious mounts(I have 3) on my DK(294+3), but that'd be dumb since I don't really play it.
Apparently some mounts are bugged on the website, like the DK's Acherus mount and Brown Horse, they need to be added to your collection manually. (not added before picture)
There's even more bugged ones on horde (Chauffeured Mechano-Hog and Swift Warstrider).
The Vash'jir Seahorse is NOT account wide, you have to complete the quest per toon.
So, check it and add them, they will line up.
The website knows what it's missing, those are accounted for.
Ok.. so what's the problem you're asking? Lol
I explained it, class mounts count but only on that character. Vicious mounts count on that character only.
So, paladins are the best to have.