It appears that the two new store mounts, Alabaster Stormtalon and Alabaster Thunderwing, are missing from the APIs. They are missing from both the mounts list, as well as from the character data.
Example 1 (I can’t post links):
Notice the list does not include Alabaster Stormtalon nor Alabaster Thunderwing
This issue was reported by a user, so I don’t want to give away their character name, but so that you can see the API call:
Again, the collected mounts list will be missing these two store mounts, even though they are collected.
Edit: I did some more digging, and wanted to add that the “Sylverian Dreamer” appears to be missing from the APIs as well. Thank you.