This has been an issue since at least December 19th, 2022 (a Monday lol), the last known date that my pet collection data was updated on Xu-Fu’s Pet Guides – which relies on the API provided by Blizzard’s website for World of Warcraft. So, to be clear, the issue is on Blizzard’s end and not Aranesh’s.
I’m putting this out here finally despite the holiday down-time just so there can be an existing thread in case someone else comes looking wondering what’s going on. Hopefully the problem will be fixed soon after New Year’s is over, since people rely on current data in order to find the pet strategy that may best suit their needs on third-party websites.
P.S. Guess I’d better mention mount collectors here so no one feels left out. 