Since the armory is basically in eternal beta what you see is not always what the sites requesting information from it will receive. As a rule of thumb it's usually the data sent to third party requests that is more accurate.
Glancing over your collection, it's probably the Sky Lantern that's causing the mismatch. The armory still doesn't have this pet listed while WarcraftPets does. Silly armory, it needs to catch up with the times.
Feel free to browse through Perks N Peeves, my vanity pet collecting blog!